[424B5] WESTLAKE CORP Prospectus Supplement (Debt Securities)

Filing Impact

(Low)

Filing Sentiment

(Neutral)

Form Type

424B5

Rhea-AI Filing Summary

Westlake Corporation launched a primary debt offering of two series of senior unsecured notes under an effective shelf. Final sizes, coupons and maturities will be set at pricing. The notes will be issued in $2,000 minimum denominations and will not be listed on an exchange.

Westlake intends to use the net proceeds to fund a cash tender offer for its 3.600% Senior Notes due 2026, of which $750 million was outstanding as of September 30, 2025. Any remaining proceeds are expected to fund the €82.5 million pending ACI acquisition and for general corporate purposes. The tender offer is expected to expire on November 10, 2025 and is conditioned on completion of this offering; the offering is not contingent on tender completion.

The notes rank equally with Westlake’s other senior unsecured debt and are effectively subordinated to secured debt and subsidiary liabilities. Westlake may redeem the notes at its option as described, and a Change of Control Triggering Event would require a 101% repurchase offer. Settlement will be in book-entry form through DTC, Euroclear and Clearstream.

11/04/2025 - 09:22 AM

Filed Pursuant to Rule 424(b)(5)
Registration No. 333-291208

This preliminary prospectus supplement and the accompanying prospectus relate to an effective registration statement under the Securities Act of 1933, as amended, but are not complete and may be changed. This preliminary prospectus supplement and the accompanying prospectus are not an offer to sell these securities and are not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

SUBJECT TO COMPLETION, DATED NOVEMBER 4, 2025

PRELIMINARY PROSPECTUS SUPPLEMENT

(To prospectus dated October 31, 2025)

LOGO

Westlake Corporation

$ % Senior Notes due 20

We are offering $ aggregate principal amount of our % Senior Notes due 20 (the “20 notes”) and $ aggregate principal amount of our % Senior Notes due 20 (the “20 notes” and, together with the 20 notes, the “notes”).

The 20 notes will mature on , 20 , and the 20 notes will mature on , 20 . The 20 notes will accrue interest at a rate of % per annum, and the 20 notes will accrue interest at a rate of % per annum. Interest on each series of the notes will accrue from November , 2025 and will be payable semi-annually in arrears on and of each year, beginning , 2026.

We may redeem the notes at our option, in whole or in part, at any time prior to their maturity at the applicable redemption price described under “Description of the Senior Notes—Optional Redemption.” If a change of control triggering event as described under “Description of the Senior Notes—Change of Control Triggering Event” occurs, we will be required, unless we have exercised our right to redeem the notes, to offer to purchase the notes from the holders.

The notes will be our senior unsecured obligations and will rank equally in right of payment with all of our other senior unsecured indebtedness from time to time outstanding. The notes will be effectively subordinated to any secured indebtedness to the extent of the value of the assets securing such indebtedness and to the indebtedness and other liabilities of our subsidiaries.

The notes will be issued only in registered form in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof in book-entry form only.

Investing in the notes involves risks. See “Risk Factors” beginning on page S-6 of this prospectus supplement, as well as the risks set forth in our filings with the Securities and Exchange Commission that are incorporated by reference into this prospectus supplement, to read about important factors you should consider carefully before investing in the notes.

Per 20
Note

Total

Per 20
Note

Total

Combined
Total for
the Notes

Public offering price (1)

Underwriting discount

Proceeds, before expenses, to us (1)

(1)	Plus accrued interest, if any, from November , 2025, if settlement occurs after that date.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We do not intend to apply for listing of the notes of either series on any securities exchange or for inclusion of the notes of either series on any automated dealer quotation system. We expect that delivery of the notes, in book-entry form only through the facilities of The Depository Trust Company for the accounts of its participants, including Euroclear Bank S.A./N.V., as operator of the Euroclear System, and Clearstream Banking, société anonyme, will be made on or about November , 2025.

Joint Book-Running Managers


BofA Securities		Deutsche Bank Securities		J.P. Morgan		Wells Fargo Securities

The date of this prospectus supplement is November , 2025

This prospectus supplement is part of a registration statement we filed with the Securities and Exchange Commission (the “SEC”). In making your decision whether to participate in this offering, you should rely only on the information contained in or incorporated by reference into this prospectus supplement and the accompanying prospectus. We have not, and the underwriters have not, authorized any person to provide you with any additional or different information. We and the underwriters take no responsibility for, and can provide no assurance as to the reliability of, any information that others may give you. This prospectus supplement and the accompanying prospectus may only be used where it is legal to offer and sell the notes, and this prospectus supplement and the accompanying prospectus are not an offer to sell or a solicitation of an offer to purchase the notes in any jurisdiction where such an offer, solicitation or sale would be unlawful. The information contained in this prospectus supplement or the accompanying prospectus is current only as of the date of this prospectus supplement or the accompanying prospectus, as the case may be, and any information incorporated by reference is current only as of the date of the document incorporated by reference. Our business, financial condition, results of operations and prospects may have changed since those respective dates.

We expect that delivery of the notes will be made to investors on or about November , 2025, which will be the business day following the date of pricing the notes (such settlement being referred to as “T+ ”). Under Rule 15c6-1 under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), trades in the secondary market generally are required to settle in one business day unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade the notes on any date prior to the business day before delivery will be required, by virtue of the fact that the notes initially will settle in T+ , to specify an alternative settlement cycle at the time of any such trade to prevent failed settlement and should consult their own advisors.

TABLE OF CONTENTS

Prospectus Supplement


	Page
CAUTIONARY STATEMENT ABOUT FORWARD-LOOKING STATEMENTS		S-ii
ABOUT THIS PROSPECTUS SUPPLEMENT		S-v
PRODUCTION CAPACITY		S-v
SUMMARY		S-1
RISK FACTORS		S-6
USE OF PROCEEDS		S-10
CAPITALIZATION		S-11
DESCRIPTION OF THE SENIOR NOTES		S-12
MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS		S-29
UNDERWRITING		S-34
LEGAL MATTERS		S-42
EXPERTS		S-42
WHERE YOU CAN FIND MORE INFORMATION		S-42

Prospectus


	Page
ABOUT THIS PROSPECTUS		1
ABOUT WESTLAKE CORPORATION		1
POTENTIAL SUBSIDIARY GUARANTORS		2
RISK FACTORS		3
CAUTIONARY STATEMENTS ABOUT FORWARD-LOOKING STATEMENTS		8
USE OF PROCEEDS		11
DESCRIPTION OF DEBT SECURITIES		12
DESCRIPTION OF CAPITAL STOCK		20
DESCRIPTION OF WARRANTS		26
SELLING STOCKHOLDER		27
PLAN OF DISTRIBUTION		28
LEGAL MATTERS		30
EXPERTS		30
WHERE YOU CAN FIND MORE INFORMATION		30

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CAUTIONARY STATEMENT ABOUT FORWARD-LOOKING STATEMENTS

The Private Securities Litigation Reform Act of 1995 provides safe harbor provisions for forward-looking information. Certain of the statements contained in this prospectus supplement and the accompanying prospectus are forward-looking statements. All statements, other than statements of historical facts, included in this prospectus supplement and the accompanying prospectus that address activities, events or developments that we expect, project, believe or anticipate will or may occur in the future are forward-looking statements. Forward-looking statements can be identified by the use of words such as “believes,” “intends,” “may,” “should,” “could,” “anticipates,” “expected” or comparable terminology, or by discussions of strategies or trends. Although we believe that the expectations reflected in such forward-looking statements are reasonable, we cannot give any assurances that these expectations will prove to be correct. Forward-looking statements relate to matters such as:

•

the expected timing for completion of the Tender Offer (as defined herein) and the sources of financing therefor;

•

our proposed acquisition of ACI (as defined herein) and the expected timing of the closing of the ACI Acquisition (as defined herein);

•

the ultimate timing, outcome and results of integrating the operations of any acquisitions and the ultimate outcome of our operating efficiencies applied to the products and services; the effects of any such acquisition, including the combined company’s future financial condition, results of operations, strategy and plans; and expected synergies and other benefits from any such acquisition and our ability to realize such synergies and other benefits;

•

recoverability of the carrying value of our long-lived assets, including tangible assets and intangible assets with finite lives, and the fair value of our reporting units with goodwill;

•

future operating rates, margins, cash flows and demand for our products;

•

industry market outlook, including the price of crude oil, natural gas, ethane, housing starts and repair and remodeling activity;

•

macroeconomic outlook, including elevated interest rates, inflation and possible recession;

•

widespread outbreak of an illness or any other communicable disease, or any other public health crisis;

•

production capacities;

•

the impact of ongoing conflicts in the Middle East and between Russia and Ukraine;

•

currency devaluation;

•

our ability to borrow under our credit agreement;

•

our ability to meet our liquidity needs;

•

our ability to meet debt obligations under our debt instruments;

•

our intended quarterly dividends;

•

future capacity additions and expansions in the industries in which we compete;

•

timing, funding and results of capital projects;

•

pension plan obligations, funding requirements and investment policies;

•

compliance with present and future environmental regulations and costs associated with environmentally related penalties, capital expenditures, remedial actions and proceedings, including any new laws, regulations or treaties that may come into force to limit or control carbon dioxide and other greenhouse gas emissions or to address other issues of climate change;

•

recovery of losses under our insurance policies;

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•

effects of pending legal proceedings and settlements;

•

timing of and amount of capital expenditures;

•

increased costs and other effects of tariffs imposed by the U.S. government, and any effects on trading relationships among the United States and other countries; and

•

results of the closure of the Pernis, Netherlands facility and cessation of operations of the PVC resin unit at the Suzhou Huasu Plastics plant located in China (such as timing and amount of recognition of related costs and our expectations regarding our financial performance following such closure and cessation of operations).

We have based these statements on assumptions and analyses in light of our experience and perception of historical trends, current conditions, expected future developments and other factors we believe were appropriate in the circumstances when the statements were made. Forward-looking statements by their nature involve substantial risks and uncertainties that could significantly impact expected results, and actual future results could differ materially from those described in such statements. While it is not possible to identify all factors, we continue to face many risks and uncertainties. Among the factors that could cause actual future results to differ materially are the risks and uncertainties discussed under “Risk Factors” in this prospectus supplement and the accompanying prospectus and in our Annual Report on Form 10-K for the fiscal year ended December 31, 2024 (the “2024 Form 10-K”) and those described from time to time in our other filings with the SEC including, but not limited to, the following:

•

general economic and business conditions, including inflation, interest rates and possible recession;

•

the cyclical nature of the chemical and building products industries;

•

the availability, cost and volatility of raw materials and energy;

•

uncertainties associated with the United States, European and worldwide economies, including those due to political tensions and conflict in the Middle East, Russia and Ukraine and elsewhere;

•

uncertainties associated with pandemic infectious diseases;

•

uncertainties associated with climate change;

•

the potential impact on demand for ethylene, polyethylene and polyvinyl chloride due to initiatives such as recycling and customers seeking alternatives to polymers;

•

current and potential governmental regulatory actions in the United States and other countries;

•

industry production capacity and operating rates;

•

the supply/demand balance for our products;

•

competitive products and pricing pressures;

•

instability in the credit and financial markets;

•

access to capital markets;

•

terrorist acts;

•

operating interruptions (including leaks, explosions, fires, weather-related incidents, mechanical failure, unscheduled downtime, delays in turnaround activities, labor difficulties, transportation interruptions, spills and releases and other environmental risks);

•

changes in laws or regulations, including trade policies and tariffs imposed on or by foreign jurisdictions;

•

disruptions in global trade, including as a result of tariffs, trade restrictions, retaliatory trade measures or the effect of such actions on trading relationships between the United States and other countries;

S-iii

•

the effects of government shutdowns;

•

technological developments;

•

information systems failures and cyberattacks;

•

foreign currency exchange risks;

•

our ability to implement our business strategies; and

•

creditworthiness of our customers.

Many of such factors are beyond our ability to control or predict. Any of the factors, or a combination of these factors, could materially affect our future results of operations and the ultimate accuracy of the forward-looking statements. These forward-looking statements are not guarantees of our future performance, and our actual results and future developments may differ materially from those projected in the forward-looking statements. Management cautions against putting undue reliance on forward-looking statements or projecting any future results based on such statements or present or prior earnings levels. Every forward-looking statement speaks only as of the date of the particular statement, and we undertake no obligation to publicly update or revise any forward-looking statements.

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ABOUT THIS PROSPECTUS SUPPLEMENT

This document is in two parts. The first part is the prospectus supplement, which describes the specific terms of the notes we are offering and certain other matters relating to us and our financial condition. The second part, the accompanying prospectus, gives more general information about securities we may offer from time to time, some of which may not apply to the notes we are offering. You should read this prospectus supplement along with the accompanying prospectus, as well as the documents incorporated by reference. If the description of the offering varies between this prospectus supplement and the accompanying prospectus, you should rely on the information in this prospectus supplement.

In this prospectus supplement and the accompanying prospectus, except under the heading “Description of the Senior Notes” in this prospectus supplement, references to “Westlake,” the “Company,” “we,” “us,” and “our” refer to Westlake Corporation and its consolidated subsidiaries, unless the context indicates otherwise.

PRODUCTION CAPACITY

Unless we state otherwise, annual production capacity estimates used in this prospectus supplement and the accompanying prospectus represent rated capacity of the facilities at December 31, 2024. We calculated rated capacity by estimating the number of days in a typical year that a production unit of a plant is expected to operate, after allowing for downtime for regular maintenance, and multiplying that number by an amount equal to the unit’s optimal daily output based on the design feedstock mix. Because the rated capacity of a production unit is an estimated amount, actual production volumes may be more or less than the rated capacity.

S-v

SUMMARY

This summary highlights certain information contained elsewhere or incorporated by reference in this prospectus supplement and the accompanying prospectus. Because this is only a summary, it does not contain all of the information that is important to you. You should read this entire prospectus supplement and accompanying prospectus, as well as the documents incorporated by reference herein, including the risk factors and the financial statements and related notes included elsewhere herein and therein, before making a decision with respect to an investment in the notes. We also urge you to read Westlake’s public filings with the SEC, as they provide additional information about Westlake that you may find important.

About Westlake Corporation

Overview

We are a vertically integrated global manufacturer and marketer of performance and essential materials and housing and infrastructure products. We operate in two principal operating segments, Performance and Essential Materials and Housing and Infrastructure Products. The Performance and Essential Materials segment includes Westlake North American Vinyls, Westlake North American Chlor-alkali & Derivatives, Westlake European & Asian Chlorovinyls, Westlake Olefins, Westlake Polyethylene and Westlake Epoxy. The Housing and Infrastructure Products segment includes Westlake Royal Building Products, Westlake Pipe & Fittings, Westlake Global Compounds and Westlake Dimex. We are highly integrated along our materials chain with significant downstream integration from ethylene and chlor-alkali (chlorine and caustic soda) into vinyls, polyethylene, epoxy and styrene monomer. We also have substantial downstream integration from polyvinyl chloride (“PVC”) into our building products, PVC pipes and fittings and PVC compounds in our Housing and Infrastructure Products segment.

We are a Delaware corporation with our principal executive offices located at 2801 Post Oak Boulevard, Suite 600, Houston, Texas 77056. Our telephone number at such address is (713) 960-9111.

Recent Developments

Concurrent Tender Offer

On the date of this prospectus supplement, we commenced a cash tender offer (the “Tender Offer”) for any and all of our outstanding 3.600% Senior Notes due 2026 (the “2026 Senior Notes”), upon the terms and subject to the conditions set forth in the related offer to purchase dated the date hereof (the “Offer to Purchase”) and notice of guaranteed delivery. As of September 30, 2025, $750 million in aggregate principal amount of the 2026 Senior Notes was outstanding.

The Tender Offer is expected to expire on November 10, 2025, unless extended or earlier terminated. The Tender Offer is conditioned on the completion of this offering of the notes on terms satisfactory to us (the “Financing Condition”) and other conditions. The consummation of this offering of the notes, however, is not contingent upon the successful completion of the Tender Offer. We cannot assure you that the Tender Offer will be completed on the terms described in this prospectus supplement, or at all, nor can we assure you that the Tender Offer will result in any of the 2026 Senior Notes being tendered and accepted for purchase. See “Risk Factors—Risks Relating to the Tender Offer—The Tender Offer may not be completed as contemplated or at all.” Nothing in this prospectus supplement shall be construed as soliciting any offer to buy any security or as an offer to purchase any of the 2026 Senior Notes, as the Tender Offer is being made only to the recipients of, and upon the terms and conditions set forth in, the related Offer to Purchase and notice of guaranteed delivery. We may amend the Tender Offer in any respect or waive any condition to the Tender Offer (including the Financing Condition described above), in each case subject to applicable law.

S-1

The consideration paid in the Tender Offer for the 2026 Senior Notes that are validly tendered and accepted for purchase will be determined in the manner described in the Offer to Purchase by reference to a fixed spread over the yield to maturity of the applicable U.S. Treasury Security (the “Reference Yield”). The Reference Yield is expected to be calculated at 2:00 p.m., New York City time, on November 10, 2025, unless extended.

Whether or not the Tender Offer is consummated or fully subscribed, we and/or our affiliates reserve the right to purchase 2026 Senior Notes from time to time in the open market, in privately negotiated transactions, through tender or exchange offers or otherwise, and/or we may redeem the 2026 Senior Notes in accordance with the provisions of the indenture governing the 2026 Senior Notes. Nothing in this prospectus supplement shall constitute a notice of redemption or an obligation to issue a notice of redemption for the 2026 Senior Notes. Any such redemption would be made only pursuant to and in accordance with the terms of the indenture governing the 2026 Senior Notes.

Pending ACI Acquisition

On August 26, 2025, we announced that we had entered into an agreement to acquire (the “ACI Acquisition”) the global compounding solutions business of the ACI/Perplastic Group (collectively, “ACI”). ACI is a Portugal-based global manufacturer of specialty materials serving the wire and cable sectors. The estimated purchase price for the ACI Acquisition is approximately €82.5 million in cash, subject to certain closing date adjustments.

The ACI Acquisition is expected to close in early 2026, subject to the satisfaction of customary closing conditions, including receipt of certain regulatory approvals. The consummation of the ACI Acquisition is not subject to a financing condition.

S-2

The Offering

The following summary contains basic information about the notes and is not intended to be complete. It does not contain all the information that is important to you. For a more complete understanding of the notes, see “Description of the Senior Notes.” Capitalized terms not otherwise defined herein shall have the same meanings given them in the “Description of the Senior Notes” section of this prospectus supplement.

Issuer

Westlake Corporation.

Notes Offered

$ aggregate principal amount of % Senior Notes due 20 .

Maturity Date

, 20 for the 20 notes.

Interest Rates; Interest Payment Dates

The 20 notes will accrue interest at a rate of % per annum.

Interest on each series of the notes will accrue from November , 2025 and will be payable semi-annually in arrears on and of each year, beginning , 2026.

Ranking

The notes will be:

•

senior unsecured obligations of Westlake;

•

equal in right of payment to existing and future senior unsecured indebtedness of Westlake;

•

effectively subordinated in right of payment to any existing and future secured indebtedness of Westlake to the extent of the value of the assets securing such indebtedness;

•

senior in right of payment to existing and future subordinated indebtedness of Westlake; and

•

structurally subordinated to existing and future obligations of Westlake’s subsidiaries.

As of September 30, 2025, the notes offered hereby would have ranked effectively pari passu in right of payment with approximately $4.7 billion of Westlake’s senior unsecured indebtedness. As of September 30, 2025, Westlake had no secured indebtedness, and its subsidiaries had $12 million of outstanding long-term indebtedness.

Optional Redemption

We may redeem the notes, in whole or in part, at any time and from time to time at the applicable redemption price described under “Description of the Senior Notes—Optional Redemption.”

S-3

Change of Control Triggering Event

Upon the occurrence of a Change of Control Triggering Event (as defined under “Description of the Senior Notes—Change of Control Triggering Event”), we will be required, unless we have exercised our right to redeem the notes of either series, to offer to repurchase the notes of such series at a price equal to 101% of their principal amount, plus accrued and unpaid interest, if any, to, but not including, the date of repurchase.

Certain Indenture Provisions

The indenture pursuant to which the notes will be issued will contain covenants that will, among other things, restrict our and certain of our subsidiaries’ ability to:

•

incur certain secured indebtedness;

•

engage in certain sale and leaseback transactions; and

•

consolidate, merge or transfer all or substantially all of our assets.

These covenants will be subject to significant exceptions. See “Description of the Senior Notes—Certain Covenants.”

Form and Denomination of Notes

Each series of notes will be issued in fully registered form only and will initially be represented by one or more global notes (as defined under “Description of the Senior Notes—Book-Entry, Clearance and Settlement”) which will be deposited with a custodian for, and registered in the name of a nominee of, the Depositary (as defined under “Description of the Senior Notes—Book-Entry, Clearance and Settlement”). The notes will be issued only in registered form in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof in book-entry form only.

Absence of Established Market for Notes

Each series of notes will be a new issue of securities for which there is no established market. Accordingly, there can be no assurance that a market for the notes will develop or as to the liquidity of any market that may develop. The underwriters have advised us that they currently intend to make a market in the notes. However, they are not obligated to do so, and any market-making with respect to the notes may be discontinued without notice. We do not intend to list the notes of either series on any securities exchange or public market or include the notes of either series on any quotation system.

Use of Proceeds

S-4

price of our pending ACI Acquisition and for general corporate purposes, including working capital management. See “Summary—About Westlake Corporation—Recent Developments—Pending ACI Acquisition.” See “Use of Proceeds.”

Pending the use of proceeds described above, we intend to use the net proceeds from this offering to make short-term investments. See “Use of Proceeds.”

Further Issuances

We may, from time to time, without the consent of or notice to holders of the notes of either series, issue and sell debt securities identical to the notes of such series in all respects (other than the issue date, and, in some cases, the public offering price and, to the extent applicable, the first date of interest accrual and first interest payment date), so that such additional debt securities will be consolidated and form a single series with the notes of such series for all purposes, including voting; provided, that if any such additional notes of such series are not fungible with the notes of such series offered hereby for U.S. federal income tax purposes, such additional notes of such series will have one or more separate CUSIP numbers from the notes of such series.

Conflicts of Interest

As a result of our intended use of the net proceeds from this offering, certain of the underwriters and/or certain of their respective affiliates may receive more than 5% of the net proceeds of this offering, not including underwriting compensation, thus creating a conflict of interest within the meaning of Rule 5121 (Public Offerings of Securities with Conflicts of Interest) of the Financial Industry Regulatory Authority, Inc. (‘‘FINRA Rule 5121’’). Accordingly, this offering is being made in compliance with the requirements of FINRA Rule 5121. The appointment of a ‘‘qualified independent underwriter’’ is not necessary in connection with this offering as the notes are investment grade rated securities. See “Underwriting—Conflicts of Interest.”

Trustee

The Bank of New York Mellon Trust Company, N.A.

Governing Law

New York

Risk Factors

Investing in the notes involves certain risks. See “Risk Factors” in this prospectus supplement, in the accompanying prospectus and in the SEC filings we incorporate by reference into this prospectus supplement for a description of certain risks you should consider before investing in the notes.

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RISK FACTORS

You should carefully consider each of the following risks, the risks discussed under the heading “Risk Factors” in the accompanying prospectus and all of the information set forth or incorporated by reference in this prospectus supplement and the accompanying prospectus, including the risks described in “Item 1A. Risk Factors” of Part I of the 2024 Form 10-K and any other documents we file with the SEC that are incorporated by reference in this prospectus supplement and the accompanying prospectus, before investing in the notes.

Risks Relating to the Tender Offer

The Tender Offer may not be completed as contemplated or at all.

We will have broad discretion over the use of the net proceeds from this offering of the notes. As described in “Use of Proceeds” and “Summary—About Westlake Corporation—Recent Developments—Concurrent Tender Offer” in this prospectus supplement, we currently anticipate using the net proceeds of the offering of the notes to fund the repurchase of the 2026 Senior Notes pursuant to the Tender Offer. We anticipate using any remaining net proceeds to fund the purchase price of our pending ACI Acquisition and for general corporate purposes, including working capital management. However, we cannot predict the extent to which holders of the 2026 Senior Notes will tender their 2026 Senior Notes in the Tender Offer, and there can be no assurance that we will complete the Tender Offer as described herein, as contemplated in the Offer to Purchase, or at all, or that a significant amount of the 2026 Senior Notes will be tendered or accepted for purchase by us. Therefore, we may use the net proceeds of this offering of the notes for purposes other than those contemplated herein and such purposes may vary substantially from the current planned uses. You may not agree with how we allocate or spend the net proceeds from this offering of the notes. We may pursue other opportunities that do not result in an increase in the market value of our securities, including the market value of the notes, and may result in us incurring losses.

Risks Relating to the Notes

Our holding company structure may affect our ability to make payments on the notes. Holders of notes may be structurally subordinated to the creditors of our subsidiaries.

We currently conduct our operations through subsidiaries, and our operating income and cash flows are generated by our subsidiaries. As a result, cash we obtain from our subsidiaries is the principal source of funds necessary to meet our debt service obligations. Contractual provisions or laws, as well as our subsidiaries’ financial condition and operating requirements, may limit our ability to obtain cash from our subsidiaries that we require to pay our debt service obligations, including payments on the notes. In addition, none of our subsidiaries will guarantee the notes, and holders of the notes will have a junior position to the claims of creditors, including trade creditors and tort claimants, of such subsidiaries. We may in the future incur indebtedness guaranteed by our subsidiaries. In the event of a bankruptcy, liquidation or reorganization of any of our subsidiaries, holders of that subsidiary’s indebtedness, holders of any of our debt guaranteed by such subsidiary and such subsidiary’s trade creditors will generally be entitled to payment of their claims from the assets of the subsidiary before any assets are made available for distribution to us.

A holder’s right to receive payments on the notes is effectively subordinated to the rights of our future secured creditors to the extent of their collateral.

Holders of our future secured indebtedness will have claims that are prior to the claims of holders of the notes to the extent of the value of the assets securing that other indebtedness. In the event of any distribution or payment of our assets in any foreclosure, dissolution, winding-up, liquidation, reorganization or other bankruptcy proceeding, holders of any secured indebtedness will have prior claim to our assets that constitute their collateral. Holders of the notes will participate ratably with all holders of our senior unsecured indebtedness, and potentially with all of our other general creditors, based upon the respective amounts owed to each holder or creditor, in our

S-6

remaining assets. We may apply proceeds of certain asset sales to reduce our future secured indebtedness or other secured obligations, but such application will not permanently reduce any future ability to incur secured indebtedness and other secured obligations under the indenture in the future. In any of the foregoing events, we cannot assure you that there will be sufficient assets to pay amounts due on the notes. As a result, holders of the notes may receive less, ratably, than holders of secured indebtedness. As of September 30, 2025, we had no secured indebtedness.

A holder’s right to receive payments on the notes could be adversely affected if any of our subsidiaries declares bankruptcy, liquidates or reorganizes.

None of our subsidiaries guarantee the notes. In the event of a bankruptcy, liquidation or reorganization of any of our subsidiaries, holders of that subsidiary’s indebtedness, holders of our debt guaranteed by such subsidiary and such subsidiary’s trade creditors will generally be entitled to payment of their claims from the assets of the subsidiary before any assets are made available for distribution to us.

Our level of debt could adversely affect our ability to operate our business.

As of September 30, 2025, after giving effect to this offering and the Tender Offer (assuming that all of the outstanding 2026 Senior Notes are tendered in the Tender Offer and purchased), we would have had approximately $ billion of total outstanding debt, and such debt would have represented approximately % of our total capitalization. Our level of debt and the limitations imposed on us by our existing or future debt agreements could have significant consequences on our business and future prospects, including the following:

•

a portion of our cash flows from operations will be dedicated to the payment of interest and principal on our debt and will not be available for other purposes;

•

we may not be able to obtain necessary financing in the future for working capital, capital expenditures, acquisitions, debt service requirements or other purposes;

•

our less leveraged competitors could have a competitive advantage because they have greater flexibility to utilize their cash flows to improve their operations;

•

we may be exposed to risks inherent in interest rate fluctuations because some of our borrowings are at variable rates of interest, which would result in higher interest expense in the event of increases in interest rates;

•

we could be vulnerable in the event of a downturn in our business that would leave us less able to take advantage of significant business opportunities and to react to changes in our business and in market or industry conditions; and

•

should we pursue additional expansions of existing assets or acquisition of third-party assets, we may not be able to obtain additional liquidity at cost effective interest rates.

These factors could be magnified or accelerated to the extent we were to finance future acquisitions with significant amounts of debt.

We may redeem the notes of either series at any time.

We may redeem some or all of the notes of either series, in whole or in part, at any time prior to their maturity at the applicable redemption price in the circumstances described under “Description of the Senior Notes—Optional Redemption.” If we redeem the notes in such circumstances, you may not be able to reinvest the redemption proceeds in securities offering a comparable yield.

We may not be able to repurchase the notes upon a Change of Control Triggering Event.

If a Change of Control Triggering Event occurs, we will be required, unless we have exercised our right to redeem the notes of either series, to make an offer to repurchase the notes of such series at a price equal to 101%

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of their principal amount, plus accrued and unpaid interest, if any, to, but not including, the date of repurchase. However, we may not be able to repurchase the notes upon a Change of Control Triggering Event because we may not have sufficient funds to do so. We may also be required to offer to repurchase certain of our other debt upon a change of control, and such event may give rise to an event of default under our revolving credit facility. In addition, agreements governing indebtedness incurred in the future may restrict us from repurchasing the notes in the event of a Change of Control Triggering Event. Any failure to repurchase properly tendered notes would constitute an event of default under the indenture governing the notes, which could, in turn, cause an acceleration of our other indebtedness. See “Description of the Senior Notes—Change of Control Triggering Event.”

To service our indebtedness and fund our capital requirements, we will require a significant amount of cash. Our ability to generate cash depends on many factors beyond our control.

Our ability to make payments on, and to refinance, our indebtedness and to fund planned capital expenditures and pay cash dividends will depend on our ability to generate cash in the future, including any distributions that we may receive from Westlake Chemical Partners LP (“Westlake Partners”). This is subject to general economic, financial, currency, competitive, legislative, regulatory and other factors that are beyond our control.

Our business may not generate sufficient cash flows from operations, we may not receive sufficient distributions from Westlake Partners and currently anticipated cost savings and operating improvements may not be realized on schedule. We also generate revenues denominated in currencies other than that of our indebtedness and may have difficulty converting those revenues into the currency of our indebtedness. We may need to refinance all or a portion of our indebtedness on or before maturity. In addition, we may not be able to refinance any of our indebtedness, including our revolving credit facility and our senior notes, on commercially reasonable terms or at all. All of these factors could be magnified if we were to finance any future acquisitions with significant amounts of debt.

Changes in our credit ratings may adversely affect the value of the notes.

We cannot provide assurance as to the credit ratings that may be assigned to the notes or that any such credit ratings will remain in effect for any given period of time or that any such ratings will not be lowered, suspended or withdrawn entirely by the rating agencies, if, in each rating agency’s judgment, circumstances warrant such an action. Further, any such ratings will be limited in scope and will not address all material risks relating to an investment in the notes but rather will reflect only the view of each rating agency at the time the rating is issued. An explanation of the significance of such rating may be obtained from such rating agency. Actual or anticipated changes or downgrades in our credit ratings, including any announcement that our ratings are under further review for a downgrade, could adversely affect the market value of the notes and increase our corporate borrowing costs.

The market prices of the notes may be volatile.

The market prices of the notes will depend on many factors that may vary over time, some of which are beyond our control, including:

•

our financial performance;

•

the amount of indebtedness we have outstanding;

•

market interest rates;

•

the market for similar securities;

•

competition;

•

the size and liquidity of the market for the notes; and

•

general economic conditions.

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As a result of these factors, you may only be able to sell your notes at prices below those you believe to be appropriate, including prices below the price you paid for them.

There may be no active trading market for the notes, and, if one develops, it may not be liquid.

Each series of notes will constitute a new issue of securities for which there is no established trading market. We do not intend to apply for listing of the notes of either series on any securities exchange or for inclusion of the notes of either series on any automated dealer quotation system. A trading market for the notes may not develop, or if a market for the notes were to develop, the notes may trade at a discount from their original offering prices, depending upon many factors, including prevailing interest rates, the market for similar securities, general economic conditions and our financial condition. Although the underwriters have advised us that they currently intend to make a market in the notes, they are not obligated to do so, and any market-making with respect to the notes may be discontinued at any time without notice. In addition, market-making activity will be subject to the limits imposed by the Securities Act of 1933, as amended (the “Securities Act”). There can be no assurance that a market for the notes will develop or as to the liquidity of any market that may develop, the ability of the holders to sell their notes or the prices at which the holders would be able to sell their notes.

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USE OF PROCEEDS

We estimate that the net proceeds from this offering will be approximately $ after deducting the underwriting discounts but before deducting estimated offering expenses payable by us. We intend to use the net proceeds from this offering to fund the repurchase of the 2026 Senior Notes, of which $750 million in aggregate principal amount was outstanding as of September 30, 2025, pursuant to the Tender Offer. See “Summary—About Westlake Corporation—Recent Developments—Concurrent Tender Offer.” We anticipate using any remaining net proceeds to fund the purchase price of our pending ACI Acquisition and for general corporate purposes, including working capital management. See “Summary—About Westlake Corporation—Recent Developments—Pending ACI Acquisition.” The 2026 Senior Notes bear interest at a rate of 3.600% per annum and mature on August 15, 2026, unless earlier repurchased or redeemed.

Pending the use of proceeds described above, we intend to use the net proceeds from this offering to make short-term investments.

This offering is not contingent upon the consummation of the ACI Acquisition, and there can be no assurance that the ACI Acquisition will be consummated on the terms described herein or at all.

As a result of our intended use of the net proceeds from this offering, certain of the underwriters and/or certain of their respective affiliates may receive more than 5% of the net proceeds of this offering, not including underwriting compensation, thus creating a conflict of interest within the meaning of FINRA Rule 5121. Accordingly, this offering is being made in compliance with the requirements of FINRA Rule 5121. The appointment of a ‘‘qualified independent underwriter’’ is not necessary in connection with this offering as the notes are investment grade rated securities. See “Underwriting—Conflicts of Interest.”

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CAPITALIZATION

The following table sets forth our unaudited cash, cash equivalents and available-for-sale securities, long-term debt, stockholders’ equity and total capitalization as of September 30, 2025:

•

on an actual basis; and

•

on an as-adjusted basis to give effect to (i) the sale of the notes offered hereby, after deducting the underwriting discount and estimated offering expenses, (ii) the application of the net proceeds therefrom to purchase the 2026 Senior Notes in the Tender Offer, as further described below in note (3), and (iii) the consummation of the pending ACI Acquisition. See “Use of Proceeds.”

You should read this table in conjunction with the sections entitled “Management’s Discussion and Analysis of Financial Conditions and Results of Operations” included in the 2024 Form 10-K and the Third Quarter 2025 Form 10-Q, and our consolidated financial statements and related notes, each of which are incorporated by reference in this prospectus supplement and the accompanying prospectus.


	September 30, 2025 (dollars in millions)
	Actual		As Adjusted (1)
Cash and cash equivalents	$	1,927	$
Available-for-sale securities		198		198

Long-term debt: (2)
Revolving credit facility due 2027		—		—
Term loans due 2026		3		3
3.600% senior notes due 2026 (3)		750		—
Loan related to tax-exempt waste disposal revenue bonds due 2027		11		11
1.625% €700 million senior notes due 2029		822		822
3.375% senior notes due 2030		300		300
3.50% senior notes due 2032		250		250
2.875% senior notes due 2041		350		350
5.00% senior notes due 2046		700		700
4.375% senior notes due 2047		500		500
3.125% senior notes due 2051		600		600
3.375% senior notes due 2061		450		450
% senior notes due 20 offered hereby		—
% senior notes due 20 offered hereby		—

Total long-term debt, principal amount		4,736
Total equity		9,938		9,938

Total capitalization	$	14,674	$

(1)

The “as adjusted” column reflects the use of the net proceeds from this offering to consummate the Tender Offer and the ACI Acquisition and the payment of fees and expenses in connection with this offering. The “as adjusted” column does not reflect the payment of accrued interest on the 2026 Senior Notes purchased in the Tender Offer.

(2)	Excludes debt issuance costs and discounts.

(3)

The “as adjusted” column assumes that all of the outstanding 2026 Senior Notes are tendered in the Tender Offer and purchased, as described in “Summary—About Westlake Corporation—Recent Developments—Concurrent Tender Offer.” Actual amounts purchased will depend on actual participation in the Tender Offer.

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DESCRIPTION OF THE SENIOR NOTES

The following description is a summary of the material provisions of the indenture governing the notes and does not purport to be complete and is subject to, and is qualified in its entirety by reference to, all the provisions of the indenture. Copies of the indenture are available as set forth below under “Where You Can Find More Information.” Certain defined terms used in this description but not defined below have the meanings assigned to them in the indenture. In this description, the words “Westlake,” “we,” “us” and “our” refer only to Westlake Corporation and not to any of its subsidiaries.

General

Westlake will issue the notes under an indenture, dated as of January 1, 2006, among itself, the Subsidiary Guarantors (as defined therein) and The Bank of New York Mellon Trust Company, N.A. (as successor to JPMorgan Chase Bank, National Association), as trustee, as supplemented, and as to be further supplemented in connection with establishing the terms of the notes (the “indenture”). The terms of the notes include those stated in the indenture and those made part of the indenture by reference to the Trust Indenture Act of 1939, as amended. Each series of notes is a separate series of “senior debt securities” described in the accompanying prospectus, and this summary supplements that description.

The indenture does not limit the amount of debt securities that may be issued under the indenture. As of September 30, 2025, approximately $4.7 billion of debt securities were outstanding under the indenture. We may issue additional debt securities under the indenture from time to time in one or more series. We may from time to time, without giving notice to or seeking the consent of the holders of the notes of either series offered hereby, issue additional notes of such series having the same terms (except for the issue date, and, in some cases, the public offering price and, to the extent applicable, the first date of interest accrual and the first interest payment date) as, and ranking equally and ratably with, the notes of such series offered hereby; provided that if any such additional notes of such series are not fungible with the notes of such series offered hereby for U.S. federal income tax purposes, such additional notes of such series will have one or more separate CUSIP numbers from the notes of such series. Any additional notes of such series having such similar terms, together with the notes of such series offered hereby, will constitute a single series of securities under the indenture, including for purposes of voting. No such additional notes of such series may be issued if an “event of default” (as such term is defined below) has occurred and is continuing with respect to the notes of such series offered hereby.

The registered holder of a note will be treated as the owner of the note for all purposes. Only registered holders will have rights under the indenture.

Principal, Maturity and Interest

The 20 notes are initially limited to $ in aggregate principal amount, and the 20 notes are initially limited to $ in aggregate principal amount. The 20 notes will mature on , 20 , and the 20 notes will mature on , 20 . The 20 notes will accrue interest at a rate of % per annum, and the 20 notes will accrue interest at a rate of % per annum. Interest on each series of the notes will accrue from November , 2025 and will be payable semi-annually in arrears on and of each year, beginning , 2026. Westlake will make each interest payment to the holders of record on the immediately preceding and (whether or not a business day).

Interest on the notes will accrue from the date of original issuance or, if interest has already been paid or duly provided for, from the date it was most recently paid or duly provided for. Interest will be computed on the basis of a 360-day year of twelve 30-day months. If the principal of or any premium or interest on the notes is payable on a day that is not a business day, the payment will be made on the following business day, and no interest shall accrue for the intervening period. For these purposes, a “business day” is any day that is not a Saturday, a Sunday

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or a day on which banking institutions in any of New York, New York or Houston, Texas is authorized or obligated by law, regulation or executive order to remain closed.

The notes will be issued in denominations of $2,000 and integral multiples of $1,000 in excess thereof in book-entry form only. See “—Book-Entry, Clearance and Settlement.”

Ranking

The notes will be senior unsecured obligations of Westlake and will rank equally in right of payment with all existing and future unsecured and unsubordinated obligations of Westlake. As of September 30, 2025, we had an aggregate of approximately $4.7 billion of unsecured and unsubordinated indebtedness.

The notes will effectively rank junior to all existing and future secured indebtedness of Westlake to the extent of the value of the assets securing such indebtedness. As of September 30, 2025, Westlake did not have any secured indebtedness. As of September 30, 2025, Westlake had no borrowings outstanding and no outstanding letters of credit under its revolving credit facility and had $1.5 billion of borrowing availability under its revolving credit facility. In the event of any distribution or payment of Westlake’s or its subsidiaries’ assets in any foreclosure, dissolution, winding-up, liquidation, reorganization or other bankruptcy proceeding, holders of secured indebtedness will have prior claim to such assets that constitute their collateral.

Holders of the notes will participate ratably with all holders of our senior unsecured indebtedness, and potentially with all of our other general creditors, based upon the respective amounts owed to each holder or creditor, in our remaining assets. See “Risk Factors—Risks Relating to the Notes—A holder’s right to receive payments on the notes is effectively subordinated to the rights of our future secured creditors to the extent of their collateral.”

In addition, none of our subsidiaries will guarantee the notes and the notes are structurally subordinated to the existing and future obligations of our subsidiaries. As of September 30, 2025, our subsidiaries had $12 million of outstanding long-term indebtedness. We may in the future incur indebtedness guaranteed by our subsidiaries. In the event of a bankruptcy, liquidation or reorganization of any of these subsidiaries, that subsidiary will pay the holders of its debt, the holders of any of our debt which is guaranteed by such subsidiary and its trade creditors before it will be able to distribute any of its assets to us. Accordingly, the notes will be effectively subordinated to creditors, including trade creditors, if any, of our subsidiaries. See “Risk Factors—Risks Relating to the Notes—Our holding company structure may affect our ability to make payments on the notes. Holders of notes may be structurally subordinated to the creditors of our subsidiaries.”

Optional Redemption

Prior to the applicable Par Call Date (as defined below), we may redeem the notes of either series at our option, in whole or in part, at any time and from time to time, at a redemption price (expressed as a percentage of principal amount and rounded to three decimal places) equal to the greater of:

(1) (a) the sum of the present values of the remaining scheduled payments of principal and interest thereon discounted to the redemption date (assuming the notes matured on the applicable Par Call Date) on a semi-annual basis (assuming a 360-day year consisting of twelve 30-day months) at the applicable Treasury Rate (as defined below) plus basis points in the case of the 20 Notes and basis points in the case of the 20 Notes, less (b) interest accrued to the date of redemption; and

(2) 100% of the principal amount of the notes to be redeemed;

plus, in either case, accrued and unpaid interest thereon to, but not including, the redemption date.

On or after the Par Call Date, we may redeem the notes of either series, in whole or in part, at any time and from time to time, at a redemption price equal to 100% of the principal amount of the notes being redeemed, plus accrued and unpaid interest thereon to, but not including, the redemption date.

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“Par Call Date” means, with respect to the 20 Notes, , 20 ( months prior to the maturity date of the 20 Notes) and with respect to the 20 Notes, , 20 ( months prior to the maturity date of the 20 Notes).

“Treasury Rate” means, with respect to any redemption date, the yield determined by us in accordance with the following two paragraphs.

The Treasury Rate shall be determined by us after 4:15 p.m., New York City time (or after such time as yields on U.S. government securities are posted daily by the Board of Governors of the Federal Reserve System), on the third business day preceding the redemption date based upon the yield or yields for the most recent day that appear after such time on such day in the most recent statistical release published by the Board of Governors of the Federal Reserve System designated as “Selected Interest Rates (Daily)—H.15” (or any successor designation or publication) (“H.15”) under the caption “U.S. government securities–Treasury constant maturities–Nominal” (or any successor caption or heading) (“H.15 TCM”). In determining the Treasury Rate, we shall select, as applicable: (1) the yield for the Treasury constant maturity on H.15 exactly equal to the period from the redemption date to the applicable Par Call Date (the “Remaining Life”); or (2) if there is no such Treasury constant maturity on H.15 exactly equal to the Remaining Life, the two yields – one yield corresponding to the Treasury constant maturity on H.15 immediately shorter than and one yield corresponding to the Treasury constant maturity on H.15 immediately longer than the Remaining Life – and shall interpolate to the applicable Par Call Date on a straight-line basis (using the actual number of days) using such yields and rounding the result to three decimal places; or (3) if there is no such Treasury constant maturity on H.15 shorter than or longer than the Remaining Life, the yield for the single Treasury constant maturity on H.15 closest to the Remaining Life. For purposes of this paragraph, the applicable Treasury constant maturity or maturities on H.15 shall be deemed to have a maturity date equal to the relevant number of months or years, as applicable, of such Treasury constant maturity from the redemption date.

If on the third business day preceding the redemption date H.15 TCM is no longer published, we shall calculate the Treasury Rate based on the rate per annum equal to the semi-annual equivalent yield to maturity at 11:00 a.m., New York City time, on the second business day preceding such redemption date of the United States Treasury security maturing on, or with a maturity that is closest to, the applicable Par Call Date, as applicable. If there is no United States Treasury security maturing on the applicable Par Call Date but there are two or more United States Treasury securities with a maturity date equally distant from the applicable Par Call Date, one with a maturity date preceding the applicable Par Call Date and one with a maturity date following the applicable Par Call Date, we shall select the United States Treasury security with a maturity date preceding the applicable Par Call Date. If there are two or more United States Treasury securities maturing on the applicable Par Call Date or two or more United States Treasury securities meeting the criteria of the preceding sentence, we shall select from among these two or more United States Treasury securities the United States Treasury security that is trading closest to par based upon the average of the bid and asked prices for such United States Treasury securities at 11:00 a.m., New York City time. In determining the Treasury Rate in accordance with the terms of this paragraph, the semi-annual yield to maturity of the applicable United States Treasury security shall be based upon the average of the bid and asked prices (expressed as a percentage of principal amount) at 11:00 a.m., New York City time, of such United States Treasury security, and rounded to three decimal places.

Our actions and determinations in determining the redemption price shall be conclusive and binding for all purposes, absent manifest error. The trustee shall have no responsibility to calculate or determine the redemption price or the Treasury Rate.

We will deliver notice of a redemption not less than 10 days nor more than 60 days before the redemption date to holders of notes to be redeemed. Once notice of redemption is sent, the notes called for redemption will become due and payable on the redemption date at the applicable redemption price.

If we elect to redeem less than all of the notes of either series, the particular notes or portions thereof for redemption will be selected from the outstanding notes of such series not previously called for redemption by lot.

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If we elect to redeem less than all of the notes of either series and such notes are at the time represented by a global note, then the depositary will select in accordance with the depositary’s standard procedures the particular notes to be redeemed. Notes may be selected for redemption in principal amounts of $1,000 and integral multiples of $1,000 in excess thereof, provided that the unredeemed portion of a note must be in a minimum principal amount of $2,000.

Notice of any redemption of the notes may, at our discretion, be given subject to one or more conditions precedent, including, but not limited to, completion of a corporate transaction that is pending (such as an equity or equity-linked offering, an incurrence of indebtedness or an acquisition or other strategic transaction involving a change of control in us or another entity). If such redemption is so subject to satisfaction of one or more conditions precedent, such notice shall describe each such condition, and such notice may be rescinded in the event that any or all such conditions shall not have been satisfied or otherwise waived on or prior to the business day immediately preceding the relevant redemption date. We shall notify holders of notes called for redemption of any such rescission as soon as practicable after we determine that such conditions precedent will not be able to be satisfied or we are not able or willing to waive such conditions precedent.

Unless there is a default in payment of the redemption price, on and after the redemption date, interest will cease to accrue on the notes or portions thereof called for redemption.

We may at any time, and from time to time, purchase the notes of either series at any price or prices in the open market, through negotiated transactions, by tender offer or otherwise.

Sinking Fund

The notes will not be entitled to any sinking fund.

Change of Control Triggering Event

Upon the occurrence of a Change of Control Triggering Event, unless we have exercised our right to redeem the notes of either series as described under “—Optional Redemption” in accordance with the indenture, each holder of the notes of such series will have the right to require us to purchase all or a portion ($1,000 or an integral multiple of $1,000 in excess thereof) of such holder’s notes of such series pursuant to the offer described below (the “Change of Control Offer”), at a purchase price equal to 101% of the principal amount thereof, plus accrued and unpaid interest, if any, to, but not including, the date of purchase (the “Change of Control Payment”), subject to the rights of holders of the notes of such series on the relevant record date to receive interest due on the relevant interest payment date; provided that the principal amount of a note of such series remaining outstanding after a repurchase in part shall be $2,000 or an integral multiple of $1,000 in excess thereof.

Within 30 days following the date upon which the Change of Control Triggering Event occurred, or at our option, prior to any Change of Control but after the public announcement of the pending Change of Control, we will be required to deliver a notice to each holder of the notes not redeemed, with a copy to the trustee, which notice will govern the terms of the Change of Control Offer. Such notice will, among other things, state the purchase date, which must be no earlier than 30 days nor later than 60 days from the date such notice is sent, other than as may be required by applicable law (the “Change of Control Payment Date”), describe the transaction or transactions constituting the Change of Control Triggering Event and offer to repurchase the notes. The notice, if sent prior to the date of consummation of the Change of Control, will state that the Change of Control Offer is conditioned on the Change of Control being consummated on or prior to the Change of Control Payment Date.

On the Change of Control Payment Date, we will, to the extent lawful:

•

accept or cause a third party to accept for payment all notes or portions of notes properly tendered pursuant to the Change of Control Offer;

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•

deposit or cause a third party to deposit with the paying agent an amount equal to the Change of Control Payment in respect of all notes or portions of notes properly tendered; and

•

deliver or cause to be delivered to the trustee the notes to be redeemed properly accepted together with an officers’ certificate stating the aggregate principal amount of notes or portions of notes being repurchased and that all conditions precedent to the Change of Control Offer and to the repurchase by us of notes pursuant to the Change of Control Offer have been complied with.

We will not be required to make a Change of Control Offer with respect to the notes of either series if (i) a third party makes such an offer in the manner, at the times and otherwise in compliance with the requirements for such an offer otherwise required to be made by us and such third party purchases all such notes of such series properly tendered and not withdrawn under its offer or (ii) a notice of redemption has been given to the holders of all of the notes of such series in accordance with the terms of the indenture, unless and until there is a default in payment of the redemption price.

A Change of Control Offer may be made in advance of a Change of Control, conditional upon such Change of Control, if a definitive agreement is in place with respect to the Change of Control at the time of making of the Change of Control Offer.

We will comply in all material respects with the requirements of Rule 14e-1 under the Exchange Act, and any other securities laws and regulations thereunder to the extent those laws and regulations are applicable in connection with the repurchase of the notes as a result of a Change of Control Triggering Event. To the extent that the provisions of any such securities laws or regulations conflict with the Change of Control Offer provisions of the notes, we will comply with those securities laws and regulations and will not be deemed to have breached our obligations under the Change of Control Offer provisions of the notes by virtue of any such conflict.

For purposes of the foregoing discussion of a Change of Control Offer, the following definitions are applicable:

“Below Investment Grade Rating Event” with respect to the notes of either series means the rating on the notes of such series is lowered and as a result the notes of such series cease to be rated Investment Grade by each of the Rating Agencies on any date during the period (the “Trigger Period”) commencing on the earlier of (a) the occurrence of a Change of Control and (b) the first public announcement by us of any Change of Control (or pending Change of Control) and ending 60 days following the consummation of such Change of Control (which Trigger Period will be extended if the rating of the notes of such series is under publicly announced consideration for possible downgrade by any Rating Agency on such 60th day, such extension to last with respect to each Rating Agency until the date on which such Rating Agency considering such possible downgrade either (x) rates the notes of such series below Investment Grade or (y) publicly announces that it is no longer considering the notes of such series for possible downgrade; provided that no such extension will occur if on such 60th day the notes of such series are rated Investment Grade not subject to review for possible downgrade by any Rating Agency); provided that a rating event will not be deemed to have occurred in respect of a particular Change of Control (and thus will not be deemed a Below Investment Grade Rating Event for purposes of the definition of Change of Control Triggering Event) if each Rating Agency making the reduction in rating does not publicly announce or confirm or inform the trustee in writing at our request that the reduction was the result, in whole or in part, of any event or circumstance comprised of or arising as a result of, or in respect of, the Change of Control (whether or not the applicable Change of Control has occurred at the time of the Below Investment Grade Rating Event). If any Rating Agency withdraws its rating on the notes of such series or otherwise ceases to provide a rating on the notes of such series on any day during the Trigger Period for any reason and we have not selected a replacement Rating Agency pursuant to the terms of the indenture, the rating of such Rating Agency shall be deemed to be rated below an Investment Grade on such day.

“Beneficial Owner” has the meaning assigned to such term in Rule 13d-3 and Rule 13d-5 under the Exchange Act, except that in calculating the beneficial ownership of any particular “person” as such term is used in

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Section 13(d)(3) of the Exchange Act, such “person” will be deemed to have beneficial ownership of all securities that such “person” has the right to acquire by conversion or exercise of other securities, whether such right is currently exercisable or is exercisable only upon the occurrence of a subsequent condition.

“Change of Control” means the occurrence of any of the following after the date of issuance of the notes:

•

the direct or indirect sale, lease, transfer, conveyance or other disposition (other than by way of merger or consolidation), in one or a series of related transactions, of all or substantially all of the assets of Westlake and its Subsidiaries taken as a whole to any “person” or “group” (as those terms are used in Section 13(d)(3) of the Exchange Act) other than to Westlake or one of its Subsidiaries;

•

the consummation of any transaction (including, without limitation, any merger or consolidation) the result of which is that any “person” or “group” (as those terms are used in Section 13(d)(3) of the Exchange Act, it being agreed that an employee of Westlake or any of its Subsidiaries for whom shares are held under an employee stock ownership, employee retirement, employee savings or similar plan and whose shares are voted in accordance with the instructions of such employee shall not be a member of a “group” (as that term is used in Section 13(d)(3) of the Exchange Act) solely because such employee’s shares are held by a trustee under said plan) becomes the ultimate Beneficial Owner, directly or indirectly, of our Voting Stock representing more than 50% of the voting power of our outstanding Voting Stock;

•

we consolidate with, or merge with or into, any Person, or any Person consolidates with, or merges with or into, us, in any such event pursuant to a transaction in which any of our outstanding Voting Stock or Voting Stock of such other Person is converted into or exchanged for cash, securities or other property, other than any such transaction where our Voting Stock outstanding immediately prior to such transaction constitutes, or is converted into or exchanged for, Voting Stock representing more than 50% of the voting power of the Voting Stock of the surviving Person or its parent immediately after giving effect to such transaction;

•

during any period of 24 consecutive calendar months, the majority of the members of our board of directors shall no longer be composed of individuals (a) who were members of our board of directors on the first day of such period or (b) whose election or nomination to our board of directors was approved by individuals referred to in clause (a) above constituting, at the time of such election or nomination, at least a majority of our board of directors or, if directors are nominated by a committee of our board of directors, constituting at the time of such nomination, at least a majority of such committee; or

•

the adoption of a plan relating to our liquidation or dissolution.

Notwithstanding the foregoing, a transaction will not be deemed to involve a Change of Control if (i) we become a direct or indirect wholly owned subsidiary of a holding company and (ii) the direct or indirect holders of the Voting Stock of such holding company immediately following that transaction are substantially the same as the holders of our Voting Stock immediately prior to that transaction.

“Change of Control Triggering Event” with respect to the notes of either series means the occurrence of both a Change of Control and a Below Investment Grade Rating Event. Notwithstanding the foregoing, no Change of Control Triggering Event will be deemed to have occurred in connection with any particular Change of Control unless and until such Change of Control has actually been consummated.

“Fitch” means Fitch Ratings, Inc. or any successor to the rating agency business thereof.

“Investment Grade” means a rating of BBB- or better by Fitch (or its equivalent under any successor rating category of Fitch), a rating of Baa3 or better by Moody’s (or its equivalent under any successor rating category of Moody’s) and a rating of BBB- or better by S&P (or its equivalent under any successor rating category of S&P),

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and the equivalent investment grade credit rating from any replacement rating agency or rating agencies selected by us under the circumstances permitting us to select a replacement rating agency and in the manner for selecting a replacement rating agency, in each case as set forth in the definition of “Rating Agency.”

“Moody’s” means Moody’s Investors Service, Inc., a subsidiary of Moody’s Corporation, and its successors.

“Rating Agency” means each of Fitch, Moody’s and S&P; provided that if any of Fitch, Moody’s or S&P ceases to provide rating services to issuers or investors, we may appoint another “nationally recognized statistical rating organization” (as defined under the Exchange Act) as a replacement for such Rating Agency; provided that we shall give written notice of such appointment to the trustee.

“S&P” means S&P Global Ratings, a division of S&P Global Inc., and its successors.

“Voting Stock” of any specified Person as of any date means the capital stock (or comparable equity interests) of such Person that is at the time entitled to vote generally in the election of the board of directors (or members of the governing body) of such Person.

For purposes of the notes, “Person” includes any individual, corporation, limited liability company, partnership, joint venture, association, joint stock company, trust, estate, unincorporated organization or government or any agency or political subdivision thereof or any other entity.

The definition of Change of Control includes a phrase relating to the direct or indirect sale, lease, transfer, conveyance or other disposition of “all or substantially all” of the properties or assets of Westlake and its Subsidiaries taken as a whole. Although there is a limited body of case law interpreting the phrase “substantially all,” there is no precise, established definition of the phrase under applicable law. Accordingly, the applicability of the requirement that we offer to repurchase the notes as a result of a sale, lease, transfer, conveyance or other disposition of less than all of the assets of Westlake and its Subsidiaries taken as a whole to another Person or group may be uncertain.

Certain Covenants

The indenture will contain, among others, the following covenants:

Restrictions on Secured Debt

Under the indenture, Westlake will not, and we will not permit any Restricted Subsidiary (as defined below) to, incur, issue, assume or guarantee any notes, bonds, debentures or other similar evidences of indebtedness for money borrowed (“Debt”), secured by pledge of, or mortgage or lien on, any Principal Property (as defined below) of Westlake or any Restricted Subsidiary, or any shares of stock of or Debt of any Restricted Subsidiary (such pledges, mortgages and liens being called “Mortgage” or “Mortgages” and such Debt secured by such Mortgages being called “Secured Debt”), without effectively providing that the notes (together with, if we shall so determine, any other indebtedness of Westlake or such Restricted Subsidiary then existing or thereafter created which is not subordinate to the notes) shall be secured equally and ratably with (or prior to) such Secured Debt, so long as such Secured Debt shall be so secured, unless after giving effect thereto, the aggregate amount of all such Secured Debt plus all Attributable Debt of Westlake and its Restricted Subsidiaries in respect of any Sale and Leaseback Transaction (as defined below) would not, at the time of such incurrence, issuance, assumption or guarantee, exceed 15% of Consolidated Net Tangible Assets; provided, however, that this restriction shall not apply to, and there shall be excluded from Secured Debt in any computation under such restriction, indebtedness secured by:

•

Mortgages on such property or shares of stock or Debt existing on the first date the notes are originally issued;

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•

Mortgages on such property or shares of stock of or Debt of any Person, which Mortgages are existing at the time (i) such Person became a Restricted Subsidiary, (ii) such Person is merged into or consolidated with Westlake or any of its Subsidiaries or (iii) Westlake or one of its Subsidiaries merges into or consolidates with such Person (in a transaction in which such Person becomes a Restricted Subsidiary), which Mortgage was not incurred in anticipation of such transaction and was outstanding prior to such transaction;

•

Mortgages in favor of Westlake;

•

Mortgages in favor of a governmental entity or in favor of the holders of securities issued by any such entity, pursuant to any contract or statute (including Mortgages to secure debt of the pollution control or industrial revenue bond type) or to secure any indebtedness incurred for the purpose of financing all or any part of the purchase price or the cost of construction of the property subject to such Mortgages;

•

Mortgages in favor of any governmental entity to secure progress, advance or other payments pursuant to any contract or provision of any statute;

•

Mortgages on such property or shares of stock or Debt existing at the time of acquisition thereof (including acquisition through merger or consolidation);

•

Mortgages on such property or shares of stock or Debt to secure the payment of all or any part of the purchase price or construction cost thereof or to secure any Debt incurred prior to, at the time of, or within 180 days after, the acquisition of such property or shares or Debt, the completion of any construction or the commencement of full operation, for the purpose of financing all or any part of the purchase price or construction cost thereof;

•

Mortgages incurred in connection with a Sale and Leaseback Transaction satisfying the provisions described under “—Limitations on Sale and Leaseback Transactions” below; and

•

any extension, renewal or replacement (or successive extensions, renewals or replacements), as a whole or in part, of any Mortgage referred to in the foregoing bullet points; provided that such extension, renewal or replacement Mortgage shall be limited to all or a part of the same such property or shares of stock or Debt that secured the Mortgage extended, renewed or replaced (plus improvements on such property).

Limitations on Sale and Leaseback Transactions

Under the indenture, Westlake will not, and will not permit any Restricted Subsidiary to, enter into any arrangement with any bank, insurance company or other lender or investor (not including us or any Restricted Subsidiary) or to which any such lender or investor is a party, providing for the leasing by us or a Restricted Subsidiary for a period, including renewals, in excess of three years of any Principal Property the ownership of which has been or is to be sold or transferred, more than 180 days after the completion of construction and commencement of full operation thereof, by us or such Restricted Subsidiary to such lender or investor or to any Person to whom funds have been or are to be advanced by such lender or investor on the security of such Principal Property (referred to as a “Sale and Leaseback Transaction”) unless:

•

such Sale and Leaseback Transaction is with a governmental entity that provides financial or tax benefits;

•

we or such Restricted Subsidiary could create Secured Debt pursuant to the provisions described under “—Restrictions on Secured Debt” on the Principal Property to be leased in an amount equal to the Attributable Debt with respect to such Sale and Leaseback Transaction without equally and ratably securing notes issued under the indenture; or

•

(a) the net proceeds of the sale or transfer of the Principal Property leased pursuant to such Sale and Leaseback Transaction is at least equal to the fair market value of such Principal Property and (b) within 180 days after such sale or transfer shall have been made by us or by a Restricted Subsidiary,

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we apply an amount not less than the greater of (i) the net proceeds of the sale of the Principal Property leased pursuant to such arrangement or (ii) the fair market value of the Principal Property so leased at the time of entering into such arrangement (as evidenced by an officers’ certificate delivered to the trustee) to the retirement of Funded Debt (as defined below) of Westlake; provided that the amount to be applied to the retirement of Funded Debt of Westlake shall be reduced by (x) the principal amount of notes issued under the indenture delivered within 180 days after such sale to the trustee for retirement and cancellation, and (y) the principal amount of Funded Debt other than notes issued under the indenture, voluntarily retired by us within 180 days after such sale. No retirement referred to in this bullet point may be effected by payment at maturity or pursuant to any mandatory sinking fund payment or mandatory prepayment provision.

Limitations on Consolidations, Mergers and Sales of Assets

The indenture will provide that we may not consolidate with or merge into any entity or sell, lease, convey, assign, transfer or dispose of all or substantially all of our assets to any entity unless:

(1)

the resulting, surviving or transferee Person is either Westlake or is a corporation organized under the laws of the United States, any state thereof or the District of Columbia, and, if not Westlake, the resulting entity assumes by a supplemental indenture the due and punctual payments on the notes and the performance of our covenants and obligations under the indenture; and

(2)

immediately after giving effect to the transaction, no default or event of default under the indenture has occurred and is continuing or would result from the transaction.

Upon any transaction of the type described above, the resulting entity will succeed to and be substituted for and may exercise all of our rights and powers under the indenture and the notes with the same effect as if the resulting entity had been named as us in the indenture. In the case of any asset transfer or disposition other than a lease, when the resulting entity assumes all of our obligations and covenants under the indenture and the notes, we will be relieved of all such obligations.

Certain Definitions

“Attributable Debt” means, as to any lease in respect of a Sale and Leaseback Transaction under which any Person is at the time liable, at any date as of which the amount thereof is to be determined, the total net amount of rent required to be paid by such Person under such lease during the remaining term thereof (or, if earlier, the first date upon which such lease may be terminated without penalty), discounted from the respective due dates thereof to such date at the weighted average rate per annum borne by the notes, compounded annually. The net amount of rent required to be paid under any such lease for any such period shall be the aggregate amount of the rent payable by the lessee with respect to such period after excluding amounts required to be paid on account of maintenance and repairs, insurance, taxes, assessments, water rates and similar charges. Unless we elect to calculate the total amount of rent required to be paid through the first date upon which such lease may be terminated without penalty (if such a provision exists), in the case of any lease which is terminable by the lessee upon the payment of a penalty, such net amount shall also include the amount of such penalty, but no rent shall be considered as required to be paid under such lease subsequent to the first date upon which it may be so terminated.

“Consolidated Net Tangible Assets” means the aggregate amount of assets (less operating leases, applicable reserves and other properly deductible items) after deducting therefrom (a) all current liabilities, except for (i) notes and loans payable, (ii) current maturities of long-term debt and (iii) current maturities of obligations under finance leases and operating leases and (b) all goodwill, trade names, trademarks, patents, unamortized debt discount and expense, turnaround costs and other like intangibles, all as set forth on the most recent balance sheet of Westlake and its consolidated Subsidiaries and computed in accordance with generally accepted accounting principles in the United States as in effect from time to time (“GAAP”). Deferred income taxes,

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deferred investment tax credit or other similar items, as calculated in accordance with GAAP, will not be considered as a liability or as a deduction from or adjustment to total assets.

“Funded Debt” means all indebtedness for money borrowed having a maturity of more than 12 months from the date of the most recent balance sheet of Westlake and its consolidated Subsidiaries or having a maturity of less than 12 months but by its terms being renewable or extendible beyond 12 months from the date of such balance sheet at the option of the borrower of such indebtedness.

“Principal Property” means any single parcel of real estate, any single manufacturing plant or any single warehouse owned or leased in connection with a Sale and Leaseback Transaction by Westlake or any Subsidiary which is located within the United States and the net book value of which on the date as of which the determination is being made exceeds 1% of Consolidated Net Tangible Assets, other than any such manufacturing plant or warehouse or portion thereof (a) which is a pollution control or other facility financed by obligations issued by a state or local government unit and described in Sections 141(a), 142(a)(5), 142(a)(6), 142(a)(10) or 144(a) of the Internal Revenue Code of 1986, as amended (the “Code”), (or their successor provisions) or by any other obligations the interest of which is excluded under Section 103 of the Code (or its successor provision), or (b) which, in the good-faith opinion of our board of directors, as evidenced by a board resolution, is not of material importance to the total business conducted by Westlake and its Subsidiaries taken as a whole. As of September 30, 2025, Westlake and its Restricted Subsidiaries had Principal Properties representing approximately 22.6% of Westlake’s consolidated assets as of such date.

“Restricted Subsidiary” means a wholly owned Subsidiary of Westlake, substantially all of the assets of which are located in the United States (excluding territories or possessions), and which owns a Principal Property; provided, however, that the term Restricted Subsidiary shall not include any Subsidiary that is principally engaged in (a) the business of financing; (b) the business of owning, buying, selling, leasing, dealing in or developing real property; or (c) the business of exporting goods or merchandise from or importing goods or merchandise into the United States.

“Subsidiary” means a Person more than 50% of the outstanding Voting Stock (as defined above) of which is owned, directly or indirectly, by Westlake or by one or more other Subsidiaries, or by Westlake and one or more other Subsidiaries.

Events of Default

The following are “events of default” with respect to each series of notes:

•

our failure to pay interest on the notes of such series for 30 days after becoming due;

•

our failure to pay principal of or any premium on the notes of such series when due;

•

our failure to comply with any covenant or agreement of the notes of such series or the indenture (other than an agreement or covenant that has been included in the indenture solely for the benefit of another series of notes) for 60 days after written notice by the trustee or by the holders of at least 25% in principal amount of the outstanding notes of such series issued under the indenture that are affected by that failure; and

•

specified events involving bankruptcy, insolvency or reorganization of Westlake.

A default under one series of notes will not necessarily be a default under any other series. If a default or event of default for either series of the notes occurs, is continuing and the trustee is notified in writing of such default or event of default, the trustee will notify the holders of the notes of such series within 90 days after receiving such notice. The trustee may withhold notice to the holders of the notes of such series of any default or event of default, except in any payment on the notes of such series, if the trustee in good faith determines that withholding notice is in the interests of the holders of the notes of such series.

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If an event of default for either series of the notes occurs and is continuing, the trustee or the holders of at least 25% in principal amount of the outstanding notes of such series (or, in some cases, 25% in principal amount of all notes issued under the indenture that are affected, voting as one class) may declare the principal of and all accrued and unpaid interest on those notes to be due and payable immediately. If an event of default relating to certain events of bankruptcy, insolvency or reorganization of Westlake occurs, the principal of and accrued and unpaid interest on the notes of such series will become immediately due and payable without any action on the part of the trustee or any holder. At any time after a declaration of acceleration has been made, the holders of a majority in principal amount of the outstanding notes of such series (or, in some cases, of all notes issued under the indenture that are affected, voting as one class) may in some cases rescind this accelerated payment requirement and its consequences.

A holder of notes may pursue any remedy under the indenture only if:

•

the holder gives the trustee written notice of a continuing event of default with respect to the notes of such series;

•

the holders of at least 25% in principal amount of the outstanding notes of such series make a written request to the trustee to pursue the remedy;

•

the holders offer to the trustee indemnity satisfactory to the trustee against any loss, liability or expense;

•

the trustee does not comply with the request within 60 days after receipt of the request and offer of indemnity; and

•

during that 60-day period, the holders of a majority in principal amount of the notes of such series do not give the trustee a direction inconsistent with the request.

This provision does not, however, affect the right of a holder of notes to sue for enforcement of any overdue payment.

The trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request or direction of any of the holders unless those holders have offered to the trustee indemnity satisfactory to it. Subject to this provision for indemnification, the holders of a majority in principal amount of the outstanding notes of either series (or a majority in principal amount of all notes issued under the indenture that are affected, voting as one class) generally may direct the time, method and place of:

•

conducting any proceeding for any remedy available to the trustee; or

•

exercising any trust or power conferred on the trustee relating to or arising as a result of an event of default.

If an event of default occurs and is continuing, the trustee will be required to use the degree of care and skill of a prudent person in the conduct of his own affairs.

The indenture requires us to furnish to the trustee annually a statement as to our performance of certain of our obligations under the indenture and as to any default in performance.

Modification and Waiver

We and the trustee may supplement or amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding notes of all series issued under the indenture that are affected by the amendment or supplement (voting as one class). Without the consent of the holder of each note affected, however, no modification may:

•

reduce the amount of notes whose holders must consent to an amendment, supplement or waiver;

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•

reduce the rate of or change the time for payment of interest on the notes;

•

reduce the principal of the notes or change their stated maturity;

•

reduce any premium payable on the redemption of the notes or change the time at which the notes may or must be redeemed;

•

change any obligation to pay additional amounts on the notes;

•

make payments on the notes payable in currency other than as originally stated in the notes;

•

impair the holder’s right to institute suit for the enforcement of any payment on or with respect to the notes;

•

make any change in the percentage of principal amount of notes necessary to waive compliance with certain provisions of the indenture or to make any change in the provision related to modification; and

•

waive a continuing default or event of default regarding any payment on the notes.

We and the trustee may supplement or amend the indenture or waive any provision of the indenture without the consent of any holders of notes issued under the indenture in certain circumstances, including:

•

to cure any ambiguity, omission, defect or inconsistency;

•

to provide for the assumption of our obligations under the indenture by a successor upon any merger, consolidation or asset transfer permitted under the indenture;

•

to provide for uncertificated notes in addition to or in place of certificated notes or to provide for bearer notes;

•

to provide any security for, or to add any guarantees of or obligors on, either series of notes;

•

to comply with any requirement to effect or maintain the qualification of the indenture under the Trust Indenture Act of 1939;

•

to add covenants that would benefit the holders of any notes or to surrender any rights we have under the indenture;

•

to add events of default with respect to either series of notes;

•

to make any change that does not adversely affect any outstanding notes of either series issued under the indenture in any material respect;

•

to establish the form or terms of any notes and to accept the appointment of a successor trustee, each as permitted under the indenture; and

•

to conform the provisions of the indenture (as amended or supplemented) or the notes to the “Description of the Senior Notes” section of this prospectus supplement.

The holders of a majority in principal amount of the outstanding notes (or, in some cases, a majority in principal amount of all notes issued under the indenture that are affected, voting as one class) may waive any existing or past default or event of default with respect to the notes. Those holders may not, however, waive any default or event of default in any payment on any note or compliance with a provision that cannot be amended or supplemented without the consent of each holder affected.

Defeasance and Discharge

Defeasance. When we use the term “defeasance,” we mean discharge from some or all of our obligations under the indenture. If we deposit with the trustee under the indenture any combination of money or government

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securities sufficient to make payments on either series of the notes on the dates those payments are due, then, at our option, either of the following will occur:

•

we will be discharged from our obligations with respect to the notes of such series (“legal defeasance”); or

•

with respect to the notes of such series, we will no longer have any obligation to comply with specified restrictive covenants, the covenant described under “—Certain Covenants—Limitations on Consolidations, Mergers and Sales of Assets” above and other specified covenants under the indenture, and the related events of default will no longer apply (“covenant defeasance”).

If either series of the notes is defeased, the holders of the notes of such series will not be entitled to the benefits of the indenture, except for obligations to register the transfer or exchange of notes, replace stolen, lost or mutilated notes or maintain paying agencies and hold money for payment in trust. In the case of covenant defeasance, our obligation to pay principal, premium and interest on the notes of such series will also survive.

We will be required to deliver to the trustee an opinion of counsel that the deposit and related defeasance would not cause the beneficial owners of the notes of such series to recognize income, gain or loss for U.S. federal income tax purposes and that the beneficial owners would be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have been the case if the deposit and related defeasance had not occurred. If we elect legal defeasance, that opinion of counsel must be based upon a ruling from the U.S. Internal Revenue Service or a change in law to that effect.

Under current U.S. federal income tax law, a legal defeasance would likely be treated as a taxable exchange of notes to be defeased for interests in the defeasance trust. As a consequence, a U.S. holder would recognize gain or loss equal to the difference between the holder’s cost or other tax basis for the notes and the value of the holder’s interest in the defeasance trust, and thereafter would be required to include in income a share of the income, gain or loss of the defeasance trust. Under current U.S. federal income tax law, covenant defeasance would not be treated as a taxable exchange of such notes.

Satisfaction and Discharge. In addition, the indenture will cease to be of further effect with respect to either series of the notes, subject to exceptions relating to compensation and indemnity of the trustee under the indenture and repayment to us of excess money or government securities, when:

•

either

•

all outstanding notes of such series have been delivered to the trustee for cancellation; or

•

all outstanding notes of such series not delivered to the trustee for cancellation either:

•

have become due and payable,

•

will become due and payable at their stated maturity within one year, or

•

are to be called for redemption within one year; and

•

we have deposited with the trustee any combination of money or government securities in trust sufficient to pay the entire indebtedness on the notes of such series when due; and

•

we have paid all other sums payable by us with respect to the notes of such series.

Governing Law

New York law will govern the indenture and the notes.

The Trustee

The Bank of New York Mellon Trust Company, N.A. (successor to JPMorgan Chase Bank, National Association) acts as the trustee under the indenture. The Bank of New York Mellon Trust Company, N.A. will act as the trustee with respect to the notes.

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The indenture contains limitations on the right of the trustee, if it or any of its affiliates is then our creditor to obtain payment of claims or to realize on certain property received for any such claim, as security or otherwise. The trustee and its affiliates are permitted to engage in other transactions with us. If, however, the trustee acquires any conflicting interest, it must eliminate that conflict or resign within 90 days after ascertaining that it has a conflicting interest and after the occurrence of a default under the indenture, unless the default has been cured, waived or otherwise eliminated within the 90-day period.

Payments and Paying Agents

We will make payments on the notes in U.S. dollars at the office of the trustee and any paying agent. At our option, however, payments may be made by wire transfer for global notes or by check mailed to the address of the person entitled to the payment as it appears in the security register. We will make interest payments to the person in whose name the note is registered at the close of business on the record date for the interest payment. The trustee under the indenture will be designated as the paying agent for payments on notes issued under the indenture. We may at any time designate additional paying agents or rescind the designation of any paying agent or approve a change in the office through which any paying agent acts.

If the principal of or any premium or interest on the notes is payable on a day that is not a business day, the payment will be made on the following business day, and no interest shall accrue for the intervening period. For these purposes, a “business day” is any day that is not a Saturday, a Sunday or a day on which banking institutions in any of New York, New York, Houston, Texas or a place of payment on the notes is authorized or obligated by law, regulation or executive order to remain closed.

Subject to the requirements of any applicable abandoned property laws, the trustee and paying agent will pay to us upon written request any money held by them for payments on the notes that remains unclaimed for two years after the date upon which that payment has become due. After payment to us, holders of notes entitled to the money must look to us for payment. In that case, all liability of the trustee or paying agent with respect to that money will cease.

Book-Entry, Clearance and Settlement

Each series of notes will be issued in the form of one or more fully registered global notes (each a “global note”) which will be deposited with, or on behalf of, The Depository Trust Company, New York, New York (the “Depositary”) and registered in the name of Cede & Co., the Depositary’s nominee. We will not issue notes in certificated form except in certain circumstances. Beneficial interests in the global notes will be represented through book-entry accounts of financial institutions acting on behalf of beneficial owners as direct and indirect participants in the Depositary (the “Depositary Participants”). Investors may elect to hold interests in the global notes through either the Depositary (in the United States) or Clearstream Banking Luxembourg S.A. (“Clearstream Luxembourg”) or Euroclear Bank S.A./N.V., as operator of the Euroclear System (“Euroclear”), (in Europe) if they are participants in those systems, or indirectly through organizations that are participants in those systems. Clearstream Luxembourg and Euroclear will hold interests on behalf of their participants through customers’ securities accounts in Clearstream Luxembourg’s and Euroclear’s names on the books of their respective depositaries, which in turn will hold such interests in customers’ securities accounts in the depositaries’ names on the books of the Depositary. At the present time, Citibank, N.A. acts as U.S. depositary for Clearstream Luxembourg and JPMorgan Chase Bank acts as U.S. depositary for Euroclear (the “U.S. Depositaries”). Beneficial interests in the global notes will be held in minimum denominations of $2,000 and integral multiples of $1,000 in excess thereof. Except as set forth below, the global notes may be transferred, in whole but not in part, only to another nominee of the Depositary or to a successor of the Depositary or its nominee.

The Depositary has advised us that it is a limited-purpose trust company organized under the New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal

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Reserve System, a “clearing corporation” within the meaning of the New York Uniform Commercial Code and a “clearing agency” registered pursuant to the provisions of Section 17A of the Exchange Act. The Depositary holds securities that its participants (“Direct Participants”) deposit with the Depositary. The Depositary also facilitates the settlement among Direct Participants of securities transactions, such as transfers and pledges, in deposited securities through electronic computerized book-entry changes in Direct Participants’ accounts, thereby eliminating the need for physical movement of securities certificates. Direct Participants include securities brokers and dealers (which may include the underwriters), banks, trust companies, clearing corporations and certain other organizations. The Depositary is owned by a number of its Direct Participants and by NYSE Euronext, Inc. and the Financial Industry Regulatory Authority, Inc. Access to the Depositary’s book-entry system is also available to others such as securities brokers and dealers, banks and trust companies that clear through or maintain a custodial relationship with a Direct Participant, either directly or indirectly (“Indirect Participants”). The rules applicable to the Depositary and its Direct Participants and Indirect Participants are on file with the SEC.

Clearstream Luxembourg has advised us that it is incorporated under the laws of Luxembourg as a professional depositary. Clearstream Luxembourg holds securities for its participating organizations, known as “Clearstream Luxembourg participants,” and facilitates the clearance and settlement of securities transactions between Clearstream Luxembourg participants through electronic book-entry changes in accounts of Clearstream Luxembourg participants, thereby eliminating the need for physical movement of certificates. Clearstream Luxembourg provides to Clearstream Luxembourg participants, among other things, services for safekeeping, administration, clearance and settlement of internationally traded securities and securities lending and borrowing. Clearstream Luxembourg interfaces with domestic markets in several countries. As a professional depositary, Clearstream Luxembourg is subject to regulation by the Luxembourg Commission for the Supervision of the Financial Sector, also known as the Commission de Surveillance du Secteur Financier. Clearstream Luxembourg participants are recognized financial institutions around the world, including underwriters, securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations. Indirect access to Clearstream Luxembourg is also available to others, such as banks, brokers, dealers and trust companies that clear through, or maintain a custodial relationship with, a Clearstream Luxembourg participant either directly or indirectly.

Distributions with respect to the notes held beneficially through Clearstream Luxembourg will be credited to the cash accounts of Clearstream Luxembourg participants in accordance with its rules and procedures, to the extent received by the U.S. depositary for Clearstream Luxembourg.

Euroclear has advised us that it was created in 1968 to hold securities for its participants, known as “Euroclear participants,” and to clear and settle transactions between Euroclear participants and between Euroclear participants and participants of certain other securities intermediaries through simultaneous electronic book-entry delivery against payment, eliminating the need for physical movement of certificates and any risk from lack of simultaneous transfers of securities and cash. Euroclear is owned by Euroclear Clearance System Public Limited Company and operated through a license agreement by Euroclear Bank S.A./N.V., known as the “Euroclear operator.” The Euroclear operator provides Euroclear participants, among other things, with safekeeping, administration, clearance and settlement, securities lending and borrowing and related services. Euroclear participants include banks (including central banks), securities brokers and dealers and other professional financial intermediaries and may include the underwriters.

Indirect access to Euroclear is also available to others that clear through or maintain a custodial relationship with a Euroclear participant, either directly or indirectly.

The Euroclear operator is regulated and examined by the Belgian Banking and Finance Commission.

Securities clearance accounts and cash accounts with the Euroclear operator are governed by the Terms and Conditions Governing Use of Euroclear and the related Operating Procedures of the Euroclear System, and

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applicable Belgian law, collectively referred to as the terms and conditions. The terms and conditions govern transfers of securities and cash within Euroclear, withdrawals of securities and cash from Euroclear, and receipts of payments with respect to securities in Euroclear. All securities in Euroclear are held on a fungible basis without attribution of specific certificates to specific securities clearance accounts. The Euroclear operator acts under the terms and conditions only on behalf of Euroclear participants, and has no record of or relationship with persons holding through Euroclear participants.

Distributions with respect to notes held beneficially through Euroclear will be credited to the cash accounts of Euroclear participants in accordance with the terms and conditions, to the extent received by the U.S. depositary for Euroclear.

If the Depositary is at any time unwilling or unable to continue as depositary and a successor depositary is not appointed by us within 90 days, we will issue the notes in definitive form in exchange for the entire global note representing such notes. In addition, we may at any time, and in our sole discretion and subject to the procedures of the Depositary, determine not to have the notes represented by global notes and, in such event, will issue notes in definitive form in exchange for the global note representing such notes. In any such instance, an owner of a beneficial interest in the global note will be entitled to physical delivery in definitive form of notes represented by such global note equal in principal amount to such beneficial interest and to have such notes registered in its name.

Title to book-entry interests in the notes will pass by book-entry registration of the transfer within the records of Clearstream Luxembourg, Euroclear or the Depositary, as the case may be, in accordance with their respective procedures. Book-entry interests in the notes may be transferred within Clearstream Luxembourg and within Euroclear and between Clearstream Luxembourg and Euroclear in accordance with procedures established for these purposes by Clearstream Luxembourg and Euroclear, as applicable. Book-entry interests in the notes may be transferred within the Depositary in accordance with procedures established for this purpose by the Depositary. Transfers of book-entry interests in the notes among Clearstream Luxembourg or Euroclear and the Depositary may be effected in accordance with procedures established for this purpose by Clearstream Luxembourg, Euroclear and the Depositary, as applicable.

Global Clearance and Settlement Procedures

Initial settlement for the notes will be made in immediately available funds. Secondary market trading between Depositary Participants will occur in the ordinary way in accordance with the Depositary’s rules and will be settled in immediately available funds using the Depositary’s Same-Day Funds Settlement System. Secondary market trading between Clearstream Luxembourg participants and Euroclear participants will occur in the ordinary way in accordance with the applicable rules and operating procedures of Clearstream Luxembourg and Euroclear, as applicable, and will be settled using the procedures applicable to conventional eurobonds in immediately available funds.

Cross-market transfers between persons holding directly or indirectly through the Depositary, on the one hand, and directly or indirectly through Clearstream Luxembourg or Euroclear, on the other, will be effected through the Depositary in accordance with the Depositary’s rules on behalf of the relevant European international clearing system by its U.S. depositary; however, such cross-market transactions will require delivery of instructions to the relevant European international clearing system by the counterparty in such system in accordance with its rules and procedures and within its established deadlines (European time).

The relevant European international clearing system will, if the transaction meets its settlement requirements, deliver instructions to its U.S. depositary to take action to effect final settlement on its behalf by delivering or receiving the notes in the Depositary and making or receiving payment in accordance with normal procedures for same-day funds settlement applicable to the Depositary. Clearstream Luxembourg participants and Euroclear participants may not deliver instructions directly to their respective U.S. depositaries.

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Because of time-zone differences, credits of the notes received in Clearstream Luxembourg or Euroclear as a result of a transaction with a Depositary Participant will be made during subsequent securities settlement processing and dated the business day following the Depositary settlement date. Such credits, or any transactions in the notes settled during such processing, will be reported to the relevant Euroclear participants or Clearstream Luxembourg participants on that business day. Cash received in Clearstream Luxembourg or Euroclear as a result of sales of notes by or through a Clearstream Luxembourg participant or a Euroclear participant to a Depositary Participant will be received with value on the business day of settlement in the Depositary but will be available in the relevant Clearstream Luxembourg or Euroclear cash account only as of the business day following settlement in the Depositary.

Although the Depositary, Clearstream Luxembourg and Euroclear have agreed to the foregoing procedures in order to facilitate transfers of the notes among Depositary Participants, Clearstream Luxembourg participants and Euroclear participants, they are under no obligation to perform or continue to perform such procedures, and such procedures may be changed or discontinued at any time.

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MATERIAL UNITED STATES FEDERAL INCOME TAX CONSIDERATIONS

The following discussion summarizes the material U.S. federal income tax consequences of the purchase, ownership and disposition of the notes by an initial holder of the notes who purchases the notes for cash at the original offering price of the applicable series of the notes and who holds the notes as “capital assets” within the meaning of Section 1221 of the Code (generally, for investment purposes). This discussion is based upon the Code, U.S. Department of the Treasury regulations promulgated under the Code (“Treasury Regulations”), and judicial decisions and administrative interpretations thereunder, all as of the date hereof and all of which are subject to change, possibly with retroactive effect, or are subject to different interpretations. We cannot assure you that the U.S. Internal Revenue Service (the “IRS”) will not challenge one or more of the tax consequences described herein, and we have not obtained, nor do we intend to obtain, a ruling from the IRS with respect to the U.S. federal income tax consequences to holders of the notes of purchasing, owning or disposing of the notes.

In this discussion, we do not purport to address all U.S. federal income tax considerations that may be important to a particular holder in light of the holder’s circumstances, such as:

•

investors that may be subject to special tax treatment, including brokers, dealers in securities or currencies, banks, financial institutions, regulated investment companies, real estate investment trusts, tax-exempt entities, retirement plans and other tax-deferred accounts, insurance companies, traders in securities that elect to use a mark-to-market method of tax accounting for their securities, or former U.S. citizens or long-term residents of the United States;

•

persons holding notes as a part of a “synthetic security”, integrated or conversion transaction or a straddle, or persons deemed to sell notes under the constructive sale provisions of the Code;

•

U.S. holders (as defined below) whose “functional currency” is not the U.S. dollar;

•

U.S. holders (as defined below) required to accelerate the recognition of any item of gross income with respect to the notes as a result of such income being recognized on an “applicable financial statement” (within the meaning of Section 451(b) of the Code);

•

U.S. holders (as defined below) who hold the notes through non-U.S. brokers or other non-U.S. intermediaries;

•

investors that hold notes through pass-through entities;

•

“controlled foreign corporations,” “passive foreign investment companies” and corporations that accumulate earnings to avoid U.S. federal income tax;

•

investors that are subject to the alternative minimum tax provisions of the Code; or

•

investors that hold our 2026 Senior Notes and participate in the Tender Offer.

This discussion also does not address the effects of other U.S. federal tax laws (such as estate and gift tax laws) or of any applicable foreign, state or local tax laws.

If a partnership (including an entity or arrangement treated as a partnership for U.S. federal income tax purposes) holds notes, the tax treatment of a partner generally will depend upon the status of the partner and upon the activities of the partnership. If you are a partner of a partnership holding notes, you are urged to consult your own tax advisors.

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YOU ARE URGED TO CONSULT YOUR OWN TAX ADVISORS AS TO THE PARTICULAR TAX CONSEQUENCES TO YOU OF THE ACQUISITION, OWNERSHIP AND DISPOSITION OF THE NOTES, INCLUDING THE EFFECT AND APPLICABILITY OF FEDERAL, STATE, LOCAL OR FOREIGN TAX LAWS OR ANY APPLICABLE INCOME TAX TREATY.

Possibility of Additional and/or Accelerated Payments

In certain circumstances (see “Description of the Senior Notes—Optional Redemption,” and “Description of the Senior Notes—Change of Control Triggering Event”), we may elect or we may be required to make payments on the notes that are in excess of the stated interest and principal on the notes. If any of those contingencies were to occur, it would affect the amount and timing of income recognized by you. Furthermore, these contingencies might implicate the provisions of the U.S. Treasury regulations relating to contingent payment debt instruments. We intend to take the position that the possibility of such contingencies occurring will not cause the notes to be treated as “contingent payment debt instruments” for U.S. federal income tax purposes. Our position may be binding on you unless you disclose a contrary position in the manner required by the applicable Treasury regulations. Assuming our position is respected, any such additional payments generally would be taxable at the time such payments are received or accrued, in accordance with your method of accounting for tax purposes. However, our position is not binding on the IRS, and it is possible that the IRS may take a different position, in which case, if the IRS’s position is sustained, you might be required to accrue ordinary interest income at a higher rate than the stated interest rate and to treat as ordinary income rather than capital gain any gain recognized on the taxable disposition of the notes. You are urged to consult your tax advisor regarding the tax consequences if the notes are treated as contingent payment debt instruments. The remainder of this discussion assumes the notes will not be treated as contingent payment debt instruments.

Consequences to U.S. Holders

You are a U.S. holder for purposes of this discussion if you are a beneficial owner of notes and you are:

•

an individual U.S. citizen or U.S. resident alien;

•

a corporation, or other entity taxable as a corporation for U.S. federal income tax purposes, that was created or organized in or under the laws of the United States, any state thereof or the District of Columbia;

•

an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

•

a trust that either (i) is subject to the supervision of a court within the United States and which has one or more “United States persons” (as defined in the Code) with authority to control all substantial decisions or (ii) has a valid election in effect under applicable Treasury Regulations to be treated as a “United States person” (as defined in the Code).

Payments of Interest

You will be required to include any stated interest payments in income in accordance with your method of accounting for U.S. federal income tax purposes. If you are a cash method taxpayer, you must report interest on the notes as ordinary income when you receive it. If you are an accrual method taxpayer, you must report the interest on the notes as ordinary income as it accrues.

Sale, Exchange, Redemption, Retirement or Other Taxable Disposition of the Notes

Upon the disposition of a note by sale, exchange, redemption, retirement or other taxable disposition, you generally will recognize capital gain or loss equal to the difference between (i) the amount realized (other than any amount representing accrued and unpaid interest, which, if not previously included in income, will be treated as interest as described above) on the disposition and (ii) your adjusted U.S. federal income tax basis in the note. Your tax basis in a note is your cost to acquire the note, subject to certain adjustments. Any capital gain or loss will be long-term capital gain or loss if you have held the note for longer than one year. The deductibility of capital losses is subject to certain limitations.

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Additional Tax on Net Investment Income

Certain U.S. holders that are individuals, trusts or estates may be subject to a 3.8% tax, in addition to otherwise applicable U.S. federal income tax, on the lesser of (i) the U.S. holder’s “net investment income” (or undistributed “net investment income,” in the case of a trust or estate) for the relevant taxable year and (ii) the excess of the U.S. holder’s modified adjusted gross income (or adjusted gross income, in the case of a trust or estate) for the relevant taxable year above a certain threshold. A U.S. holder’s “net investment income” generally includes, among other things, interest income on and gain from the disposition of securities like the notes, subject to certain exceptions. You are urged to consult your own tax advisors regarding the applicability of this tax to the notes.

Consequences to Non-U.S. Holders

You are a non-U.S. holder for purposes of this discussion if you are a beneficial owner of notes (other than an entity or arrangement treated as a partnership for U.S. federal income tax purposes) and you are not a U.S. holder.

U.S. Federal Withholding Tax

Subject to the discussion of backup withholding and FATCA below, no U.S. federal withholding tax will apply to any payment of interest on the notes provided that:

•

you do not actually or constructively own 10% or more of the total combined voting power of all classes of our stock entitled to vote;

•

you are not a “controlled foreign corporation” that is related to us, directly or indirectly, through stock ownership;

•

you are not a bank whose receipt of interest on the notes is in connection with an extension of credit made pursuant to a loan agreement entered into in the ordinary course of your trade or business;

•

interest on the notes is not effectively connected with your conduct of a U.S. trade or business; and

•

either (a) you provide to the applicable withholding agent your name and address on an IRS Form W-8BEN or IRS Form W-8BEN-E (or successor form), and certify under penalties of perjury, that you are not a U.S. person, (b) a financial institution holding the notes on your behalf certifies, under penalties of perjury, that it has received an IRS Form W-8BEN or IRS Form W-8BEN-E (or successor form) from you and provides the applicable withholding agent with a copy, or (c) you hold your notes directly through a “qualified intermediary,” and the qualified intermediary has provided to the applicable withholding agent certain documentation and has sufficient information in its files indicating that you are not a U.S. holder.

Special rules apply to foreign estates and trusts, and in certain circumstances certifications as to the foreign status of trust owners or beneficiaries may have to be provided to the applicable withholding agent.

If you cannot satisfy the requirements described above, payments of interest made to you will be subject to a 30% U.S. federal withholding tax, unless you provide the applicable withholding agent with a properly executed (1) IRS Form W-8BEN or IRS Form W-8BEN-E (or successor form) claiming an exemption from or a reduction of withholding under an applicable tax treaty or (2) IRS Form W-8ECI (or successor form) stating that interest paid on the notes is not subject to withholding tax because it is effectively connected with your conduct of a trade or business in the United States (and, in the case of an applicable tax treaty, is attributable to a U.S. permanent establishment maintained by you).

U.S. Federal Income Tax

Interest. If you are engaged in an active trade or business in the United States and interest on the notes is effectively connected with the active conduct of that trade or business (and, in the case of an applicable tax

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treaty, is attributable to a U.S. permanent establishment maintained by you), you will be subject to U.S. federal income tax on the interest on a net income basis (although you will be exempt from the 30% withholding tax if you satisfy the certification requirement by providing to the applicable withholding agent a properly executed IRS Form W-8ECI (or successor form)) in the same manner as if you were a United States person as defined under the Code. See “—Consequences to U.S. Holders” above. In addition, if you are a foreign corporation for U.S. federal income tax purposes, you may be subject to a branch profits tax equal to 30% (or lower applicable treaty rate) of your earnings and profits for the taxable year, subject to certain adjustments, including earnings and profits from an investment in the notes, that are effectively connected with the active conduct by you of a trade or business in the United States.

Sale, Exchange, Redemption, Retirement or Other Taxable Disposition of the Notes. Any gain or income realized on the sale, exchange, redemption, retirement or other taxable disposition of the notes generally will not be subject to U.S. federal income tax unless:

•

that gain or income is effectively connected with the conduct of an active trade or business in the United States by you (and, in the case of an applicable tax treaty, is attributable to a U.S. permanent establishment maintained by you);

•

you are an individual who is present in the United States for 183 days or more in the taxable year of that disposition, and certain other conditions are present; or

•

the gain represents accrued but unpaid interest, in which case the rules for taxation of interest described above in “—Consequences to Non-U.S. Holders—U.S. Federal Income Tax—Interest” would apply.

If you are a holder subject to U.S. federal income tax under the first bullet point, you will be taxed on a net income basis in the same manner as if you were a United States person as defined under the Code. See “—Consequences to U.S. Holders” above. In addition, if you are a foreign corporation for U.S. federal income tax purposes, you may be subject to a branch profits tax as explained above. Holders subject to U.S. federal income tax under the second bullet point will be taxed on the net gain at a 30% rate (or lower applicable treaty rate).

Backup Withholding and Information Reporting

U.S. Holders

Information reporting will apply to payments of principal and interest made by us on, or the proceeds of the sale or other disposition of, the notes held by you (unless you are an exempt recipient such as a corporation), and backup withholding may apply unless you provide the appropriate intermediary with your taxpayer identification number, certified under penalties of perjury, as well as certain other information or otherwise establish an exemption from backup withholding. Backup withholding is not an additional tax. Any amount withheld under the backup withholding rules is allowable as a credit against your U.S. federal income tax liability if any, and a refund may be obtained from the IRS if the amounts withheld exceed your U.S. federal income tax liability, provided the required information or appropriate claim for refund is timely provided to the IRS.

Non-U.S. Holders

Payments to non-U.S. holders of interest on a note and any amounts withheld from such payments generally will be reported to the IRS and you. Backup withholding will not apply to payments of principal and interest on the notes if you certify as to your non-U.S. holder status on an IRS Form W-8BEN or IRS Form W-8BEN-E (or successor form) under penalties of perjury or you otherwise qualify for an exemption (provided that neither we nor our agent know or have reason to know that you are a U.S. person or that the conditions of any other exemptions are not in fact satisfied).

The payment of the proceeds of the disposition of notes to or through the U.S. office of a U.S. or foreign broker will be subject to information reporting and backup withholding unless you provide the certification described

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above or you otherwise qualify for an exemption. The proceeds of a disposition effected outside the United States by a non-U.S. holder to or through a foreign office of a non-U.S. broker generally will not be subject to backup withholding or information reporting. Backup withholding is not an additional tax. Any amount withheld under the backup withholding rules is allowable as a credit against your U.S. federal income tax liability, if any, and a refund may be obtained from the IRS if the amounts withheld exceed your U.S. federal income tax liability, provided the required information or appropriate claim for refund is timely provided to the IRS.

Foreign Account Tax Compliance Act

Sections 1471 through 1474 of the Code and the Treasury Regulations and administrative guidance promulgated thereunder (commonly referred to as “FATCA”) generally impose a withholding tax of 30% on “withholdable payments” (as defined in the Code), including payments of interest with respect to debt obligations of a United States corporation, if paid to either (i) a foreign financial institution (“FFI”), whether as a beneficial owner or intermediary, unless the FFI enters into an agreement with the U.S. government to collect and provide to the U.S. tax authorities substantial information regarding U.S. account holders of such FFI (which would include certain equity and debt holders of such FFI, as well as certain account holders that are foreign entities with U.S. owners) or otherwise qualifies for an exemption from these rules or (ii) a foreign entity that is not a financial institution (whether as a beneficial owner or intermediary for another foreign entity that is not a financial institution) unless such entity provides the withholding agent or IRS with a certification identifying the substantial U.S. owners of the entity, which generally includes any U.S. person who directly or indirectly owns more than 10% of the entity, or otherwise qualifies for an exemption from these rules. While withholdable payments would have originally included payments of gross proceeds from the sale or disposition of debt obligations on or after January 1, 2019, proposed Treasury Regulations provide that such payments of gross proceeds (other than amounts treated as interest) do not constitute withholdable payments. Taxpayers may rely generally on these proposed Treasury Regulations until they are revoked or final Treasury Regulations are issued.

Foreign governments may enter into agreements with the IRS to implement FATCA in a different manner. Under certain circumstances, a beneficial owner of a debt obligation might be eligible for refunds or credits of such taxes. Investors are encouraged to consult with their own tax advisors regarding the implications of FATCA on their investment in the notes.

THE PRECEDING DISCUSSION OF U.S. FEDERAL INCOME TAX CONSIDERATIONS IS FOR GENERAL INFORMATION ONLY AND IS NOT TAX ADVICE. WE URGE EACH PROSPECTIVE INVESTOR TO CONSULT ITS OWN TAX ADVISOR REGARDING THE PARTICULAR U.S. FEDERAL, STATE, LOCAL AND FOREIGN TAX CONSEQUENCES OF PURCHASING, HOLDING AND DISPOSING OF THE NOTES.

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UNDERWRITING

BofA Securities, Inc., Deutsche Bank Securities Inc., J.P. Morgan Securities LLC and Wells Fargo Securities, LLC are each acting as representatives of the other several underwriters for this offering. Subject to the terms and conditions set forth in a firm commitment underwriting agreement among us and the underwriters, we have agreed to sell to the underwriters, and each of the underwriters has agreed, severally and not jointly, to purchase from us, the principal amount of notes set forth opposite its name below.


Underwriter	Principal Amount of 20 Notes	Principal Amount of 20 Notes
BofA Securities, Inc.	$	$
Deutsche Bank Securities Inc.
J.P. Morgan Securities LLC
Wells Fargo Securities, LLC

Total	$	$

Subject to the terms and conditions set forth in the underwriting agreement, the underwriters have agreed, severally and not jointly, to purchase all of the notes sold under the underwriting agreement if any of the notes are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the non-defaulting underwriters may be increased or the underwriting agreement may be terminated.

We have agreed to indemnify the underwriters and their controlling persons against certain liabilities in connection with this offering, including liabilities under the Securities Act, or to contribute to payments the underwriters may be required to make in respect of those liabilities.

The underwriters are offering the notes, subject to prior sale, when, as and if issued to and accepted by them, subject to approval of legal matters by their counsel, including the validity of the notes, and other conditions contained in the underwriting agreement, such as the receipt by the underwriters of officer’s certificates and legal opinions. The underwriters reserve the right to withdraw, cancel or modify offers to the public and to reject orders in whole or in part.

Commissions and Discounts

The underwriters propose to initially offer the notes directly to the public at the public offering prices set forth on the cover page of this prospectus supplement and may offer such notes to dealers at the public offering price less a concession not to exceed % of the principal amount of the 20 Notes and % of the principal amount of the 20 Notes. The underwriters may allow, and dealers may reallow, a concession not to exceed % of the principal amount of the 20 Notes and % of the principal amount of the 20 Notes. After the initial offering of the notes to the public, the underwriters may change the public offering price, concessions and other selling terms.

The expenses of the offering, not including the underwriting discount, are estimated at $ and are payable by us.

New Issue of Notes

Each series of notes is a new issue of securities with no established trading market. We do not intend to apply for listing of the notes of either series on any securities exchange or for inclusion of the notes of either series on any automated dealer quotation system. We have been advised by the underwriters that they presently intend to make a market in the notes after completion of the offering. However, they are under no obligation to do so and may discontinue any market-making activities at any time without any notice. We cannot assure the liquidity of the

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trading market for the notes or that an active public market for the notes will develop. If an active public trading market for the notes does not develop, the market price and liquidity of the notes may be adversely affected. If the notes are traded, they may trade at a discount from their initial offering price, depending on prevailing interest rates, the market for similar securities, our operating performance and financial condition, general economic conditions and other factors.

Extended Settlement

We expect that delivery of the notes will be made to investors on or about November , 2025, which will be the business day following the date of pricing the notes (such settlement being referred to as “T+ ”). Under Rule 15c6-1 under the Exchange Act, trades in the secondary market generally are required to settle in one business day unless the parties to any such trade expressly agree otherwise. Accordingly, purchasers who wish to trade the notes on any date prior to the business day before delivery will be required, by virtue of the fact that the notes initially will settle in T+ , to specify an alternative settlement cycle at the time of any such trade to prevent failed settlement and should consult their own advisors.

No Sales of Similar Securities

We have agreed that we will not, prior to the closing of the offering of the notes, without first obtaining the prior written consent of the representatives, directly or indirectly, issue, sell, offer to contract or grant any option to sell, pledge or transfer, or otherwise dispose of, any debt securities or securities exchangeable for or convertible into debt securities, except for the notes sold to the underwriters pursuant to the underwriting agreement.

Short Positions

In connection with the offering, the underwriters may purchase and sell the notes in the open market. These transactions may include short sales and purchases on the open market to cover positions created by short sales. Short sales involve the sale by the underwriters of a greater principal amount of notes than they are required to purchase in the offering. The underwriters must close out any short position by purchasing notes in the open market. A short position is more likely to be created if the underwriters are concerned that there may be downward pressure on the price of the notes in the open market after pricing that could adversely affect investors who purchase in the offering.

Similar to other purchase transactions, the underwriters’ purchases to cover the syndicate short sales may have the effect of raising or maintaining the market price of the notes or preventing or retarding a decline in the market price of the notes. As a result, the price of the notes may be higher than the price that might otherwise exist in the open market.

Neither we nor any of the underwriters make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of the notes. In addition, neither we nor any of the underwriters make any representation that the representatives will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice.

Conflicts of Interest

As a result of our intended use of the net proceeds from this offering, certain of the underwriters and/or certain of their respective affiliates may receive more than 5% of the net proceeds of this offering, not including underwriting compensation, thus creating a conflict of interest within the meaning of FINRA Rule 5121. Accordingly, this offering is being made in compliance with the requirements of FINRA Rule 5121. The appointment of a ‘‘qualified independent underwriter’’ is not necessary in connection with this offering as the notes are investment grade rated securities.

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Other Relationships

Certain of the underwriters and/or their respective affiliates have, from time to time, performed, and may in the future perform, various financial advisory, commercial banking, investment banking and other commercial services in the ordinary course of business with us or our affiliates. In particular, affiliates of certain of the underwriters are lenders and/or agents under our senior unsecured revolving credit facility. In connection with these services and transactions, the underwriters or their affiliates have received, or may in the future receive, customary fees, commissions and reimbursement of expenses.

In addition, in the ordinary course of their business activities, the underwriters and their affiliates may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for their own account and for the accounts of their customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. Certain of the underwriters or their affiliates that have a lending relationship with us routinely hedge, and certain other of those underwriters and their affiliates may hedge, their credit exposure to us consistent with their customary risk management policies. Typically, such underwriters and their affiliates would hedge such exposure by entering into transactions which consist of either the purchase of credit default swaps or the creation of short positions in our securities, including potentially the notes offered hereby. Any such credit default swaps or short positions could adversely affect future trading prices of the notes offered hereby. The underwriters and their affiliates may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

J.P. Morgan Securities LLC and Wells Fargo Securities, LLC are also acting as dealer managers in the Tender Offer and may receive compensation and reimbursement of expenses in connection therewith.

Selling Restrictions

The notes offered by this prospectus supplement may not be offered or sold, directly or indirectly, nor may this prospectus supplement or any other offering material or advertisements in connection with the offer and sale of any such notes be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus supplement. This prospectus supplement does not constitute an offer to sell or a solicitation of an offer to buy any notes offered by this prospectus supplement in any jurisdiction in which such an offer or a solicitation is unlawful.

Sales of notes in the United States by any underwriter that is not a broker-dealer registered with the SEC will be made only through one or more SEC-registered broker-dealers in compliance with applicable securities laws and the rules of FINRA.

Australia

No placement document, prospectus, product disclosure statement or other disclosure document has been lodged with the Australian Securities and Investments Commission, in relation to the offering. This prospectus supplement and accompanying prospectus do not constitute a prospectus, product disclosure statement or other disclosure document under the Corporations Act 2001 (the “Corporations Act”), and does not purport to include the information required for a prospectus, product disclosure statement or other disclosure document under the Corporations Act.

Any offer in Australia of the notes may only be made to persons (the “Exempt Investors”) who are “sophisticated investors” (within the meaning of section 708(8) of the Corporations Act), “professional investors” (within the

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meaning of section 708(11) of the Corporations Act) or otherwise pursuant to one or more exemptions contained in section 708 of the Corporations Act so that it is lawful to offer the notes without disclosure to investors under Chapter 6D of the Corporations Act.

The notes applied for by Exempt Investors in Australia must not be offered for sale in Australia in the period of 12 months after the date of allotment under the offering, except in circumstances where disclosure to investors under Chapter 6D of the Corporations Act would not be required pursuant to an exemption under section 708 of the Corporations Act or otherwise or where the offer is pursuant to a disclosure document which complies with Chapter 6D of the Corporations Act. Any person acquiring the notes must observe such Australian on-sale restrictions.

Bermuda

The notes may be offered or sold in Bermuda only in compliance with the provisions of the Investment Business Act of 2003 of Bermuda, which regulates the sale of securities in Bermuda. Additionally, non-Bermudian persons (including companies) may not carry on or engage in any trade or business in Bermuda unless such persons are permitted to do so under applicable Bermuda legislation.

Canada

The notes may be sold only to purchasers purchasing, or deemed to be purchasing, as principals that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the notes must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement and accompanying prospectus (including any amendment thereto) contain misrepresentations, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser’s province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser’s province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 (or, in the case of securities issued or guaranteed by the government of a non-Canadian jurisdiction, section 3A.4) of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriters are not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

Dubai International Financial Centre

This document relates to an Exempt Offer in accordance with the Markets Rules 2012 of the Dubai Financial Services Authority (“DFSA”). This document is intended for distribution only to persons of a type specified in the Markets Rules 2012 of the DFSA. It must not be delivered to, or relied on by, any other person. The DFSA has no responsibility for reviewing or verifying any documents in connection with Exempt Offers. The DFSA has not approved this prospectus supplement nor taken steps to verify the information set forth herein and has no responsibility for this document. The notes to which this document relates may be illiquid and/or subject to restrictions on their resale. Prospective purchasers of the notes offered should conduct their own due diligence on the notes. If you do not understand the contents of this document, you should consult an authorized financial advisor.

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In relation to its use in the Dubai International Financial Centre (“DIFC”), this document is strictly private and confidential and is being distributed to a limited number of investors and must not be provided to any person other than the original recipient, and may not be reproduced or used for any other purpose. The interests in the notes may not be offered or sold directly or indirectly to the public in the DIFC.

European Economic Area

The underwriters have not offered, sold or otherwise made available and will not offer, sell or otherwise make available any notes to any retail investor in the European Economic Area (the “EEA”). For the purposes of this provision:

(a) the expression “retail investor” means a person who is one (or more) of the following:

(i) a retail client as defined in point (11) of Article 4(1) of Directive 2014/65/EU (as amended, “MiFID II”); or

(ii) a customer within the meaning of Directive (EU) 2016/97 (as amended, the “Insurance Distribution Directive”), where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or

(iii) not a qualified investor as defined in Regulation (EU) 2017/1129 (as amended, the “Prospectus Regulation”); and

(b) the expression “offer” includes the communication in any form and by any means of sufficient information on the terms of the offer and the notes to be offered so as to enable an investor to decide to purchase or subscribe for the notes.

PRIIPs Regulation/Prohibition of sales to EEA retail investors:

The notes are not intended to be offered, sold or otherwise made available, and should not be offered, sold or otherwise made available, to any retail investor in the EEA. For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client as defined in point (11) of Article 4(1) of MiFID II; or (ii) a customer within the meaning of the Insurance Distribution Directive, where that customer would not qualify as a professional client as defined in point (10) of Article 4(1) of MiFID II; or (iii) not a qualified investor as defined in the Prospectus Regulation. Consequently, no key information document required by Regulation (EU) No 1286/2014 (as amended, the “PRIIPs Regulation”) for offering or selling the notes or otherwise making them available to retail investors in the EEA has been prepared and therefore offering or selling the notes or otherwise making them available to any retail investor in the EEA may be unlawful under the PRIIPs Regulation.

Hong Kong

The notes have not been offered or sold and will not be offered or sold in Hong Kong, by means of any document, other than (a) to “professional investors” as defined in the Securities and Futures Ordinance (Cap. 571) of Hong Kong and any rules made under that Ordinance; or (b) in other circumstances which do not result in the document being a “prospectus” as defined in the Companies Ordinance (Cap. 32) of Hong Kong or which do not constitute an offer to the public within the meaning of that Ordinance. No advertisement, invitation or document relating to the notes has been or may be issued or has been or may be in the possession of any person for the purposes of issue, whether in Hong Kong or elsewhere, which is directed at, or the contents of which are likely to be accessed or read by, the public of Hong Kong (except if permitted to do so under the securities laws of Hong Kong) other than with respect to notes which are or are intended to be disposed of only to persons outside Hong Kong or only to “professional investors” as defined in the Securities and Futures Ordinance and any rules made under that Ordinance.

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Japan

The notes have not been and will not be registered under the Financial Instruments and Exchange Law of Japan (the “Financial Instruments and Exchange Law”) and each underwriter has agreed that it will not offer or sell any notes, directly or indirectly, in Japan or to, or for the benefit of, any resident of Japan (which term as used herein means any person resident in Japan, including any corporation or other entity organized under the laws of Japan), or to others for re-offering or resale, directly or indirectly, in Japan or to a resident of Japan, except pursuant to an exemption from the registration requirements of, and otherwise in compliance with, the Financial Instruments and Exchange Law and any other applicable laws, regulations and ministerial guidelines of Japan.

People’s Republic of China

This prospectus supplement may not be circulated in the People’s Republic of China (the “PRC”) and does not constitute a public offer of the notes, whether by sale or subscription, in the PRC. The notes are not being offered or sold, directly or indirectly, in the PRC to, or for the benefit of, legal or natural persons of the PRC. Further, no legal or natural persons of the PRC may, directly or indirectly, purchase any of the notes or any beneficial interest therein without obtaining all prior PRC governmental approvals that are required, whether statutorily or otherwise. Persons who come into possession of this document are required by the Issuer and its representatives to observe these restrictions.

South Korea

The notes may not be offered, sold and delivered directly or indirectly, or offered or sold to any person for reoffering or resale, directly or indirectly, in South Korea or to any resident of South Korea except pursuant to the applicable laws and regulations of South Korea, including the Financial Investment Services and Capital Markets Act of Korea and the Foreign Exchange Transaction Act of Korea and the decrees and regulations thereunder. The notes have not been registered with the Financial Services Commission of South Korea for public offering in South Korea. Furthermore, the notes may not be re-sold to South Korean residents unless the purchaser of the notes complies with all applicable regulatory requirements (including but not limited to government approval requirements under the Foreign Exchange Transaction Act of Korea and its subordinate decrees and regulations) in connection with their purchase.

Singapore

Each underwriter has acknowledged that this prospectus supplement has not been registered as a prospectus with the Monetary Authority of Singapore. Accordingly, the underwriters have not offered or sold the notes or caused the notes to be made the subject of an invitation for subscription or purchase and will not offer or sell the notes or cause the notes to be made the subject of an invitation for subscription or purchase, and have not circulated or distributed, nor will they circulate or distribute, this prospectus supplement or any other document or material in connection with the offer or sale, or invitation for subscription or purchase, of the notes, whether directly or indirectly, to any person in Singapore other than (i) to an institutional investor (as defined in Section 4A of the Securities and Futures Act 2001 of Singapore, as modified or amended from time to time (the “SFA”)) pursuant to Section 274 of the SFA or (ii) to an accredited investor (as defined in Section 4A of the SFA) pursuant to and in accordance with the conditions specified in Section 275 of the SFA.

Switzerland

This prospectus supplement and the accompanying prospectus are not intended to constitute an offer or solicitation to purchase or invest in the notes. The notes may not be publicly offered, directly or indirectly, in Switzerland within the meaning of the Swiss Financial Services Act (“FinSA”), and no application has or will be made to admit the notes to trading on any trading venue (exchange or multilateral trading facility) in Switzerland. Neither this prospectus supplement nor accompanying prospectus nor any other offering or marketing material

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relating to the notes constitutes a prospectus pursuant to the FinSA, and neither this prospectus supplement nor accompanying prospectus nor any other offering or marketing material relating to the notes may be publicly distributed or otherwise made publicly available in Switzerland.

Taiwan

The notes have not been and will not be registered or filed with, or approved by, the Financial Supervisory Commission of Taiwan and/or any other regulatory authority of Taiwan pursuant to relevant securities laws and regulations and may not be sold, issued or offered within Taiwan through a public offering or in circumstances which could constitute an offer within the meaning of the Securities and Exchange Act of Taiwan or relevant laws and regulations that require a registration, filing or approval of the Financial Supervisory Commission of Taiwan and/or other regulatory authority of Taiwan. No person or entity in Taiwan has been authorized to offer or sell the notes in Taiwan.

United Arab Emirates

The notes have not been, and are not being, publicly offered, sold, promoted or advertised in the United Arab Emirates (including the Dubai International Financial Centre or the Abu Dhabi Global Market) other than in compliance with the regulations of the Securities and Commodities Authority and the laws of the United Arab Emirates (and the Dubai International Financial Centre and the Abu Dhabi Global Market) governing the issue, offering and sale of securities. Further, neither this prospectus supplement nor the accompanying prospectus constitutes a public offer of securities in the United Arab Emirates (including the Dubai International Financial Centre or the Abu Dhabi Global Market) and neither is intended to be a public offer. Neither this prospectus supplement nor the accompanying prospectus has been approved by or filed with (and by receiving this prospectus supplement and the accompanying prospectus the person or entity to whom it has been issued understands, acknowledges and agrees that it has not been approved by or filed with) the Central Bank of the United Arab Emirates, the Securities and Commodities Authority, the Financial Services Regulatory Authority of the Abu Dhabi Global Market, the Dubai Financial Services Authority or any other relevant licensing authorities in the United Arab Emirates.

United Kingdom

The notes are not intended to be offered, sold or otherwise made available to and should not be offered, sold or otherwise made available to any retail investor in the United Kingdom (the “UK”). For these purposes, a retail investor means a person who is one (or more) of: (i) a retail client, as defined in point (8) of Article 2 of Regulation (EU) No 2017/565 as it forms part of domestic law by virtue of the European Union (Withdrawal) Act 2018 (as amended, “EUWA”); (ii) a customer within the meaning of the provisions of the Financial Services and Markets Act 2000 (as amended, “FSMA”) and any rules or regulations made under the FSMA to implement Directive (EU) 2016/97, where that customer would not qualify as a professional client, as defined in point (8) of Article 2(1) of Regulation (EU) No 600/2014 as it forms part of domestic law by virtue of the EUWA; or (iii) not a qualified investor as defined in Article 2 of Regulation (EU) 2017/1129 as it forms part of domestic law by virtue of the EUWA (the “UK Prospectus Regulation”). Consequently, no key information document required by Regulation (EU) No 1286/2014 as it forms part of domestic law by virtue of the EUWA (the “UK PRIIPs Regulation”) for offering or selling the notes or otherwise making them available to retail investors in the UK has been prepared and therefore offering or selling the notes or otherwise making them available to any retail investor in the UK may be unlawful under the UK PRIIPs Regulation.

This prospectus supplement has been prepared on the basis that any offer of notes in the UK will be made pursuant to an exemption under the UK Prospectus Regulation from the requirement to publish a prospectus for offers of notes. This prospectus supplement is not a prospectus for the purposes of the UK Prospectus Regulation.

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This prospectus supplement is only for distribution to and directed at: (i) in the UK, persons having professional experience in matters relating to investments falling within Article 19(5) of the Financial Services and Markets Act 2000 (Financial Promotion) Order 2005 (as amended, the “Order”) and high net worth entities or other persons falling within Articles 49(2)(a) to (d) of the Order, (ii) persons who are outside the UK and (iii) any other person to whom it can otherwise be lawfully distributed (all such persons together being referred to as “Relevant Persons”). Any investment or investment activity to which this prospectus supplement relates is available only to and will be engaged in only with Relevant Persons, and any person who is not a Relevant Person should not rely on it.

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LEGAL MATTERS

Certain legal matters in connection with the offering of the notes will be passed upon for us by Baker Botts L.L.P., Houston, Texas, and will be passed upon for the underwriters by Davis Polk & Wardwell LLP, New York, New York.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control over Financial Reporting) incorporated in this prospectus supplement by reference to the Annual Report on Form 10-K for the year ended December 31, 2024 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

We file reports, proxy statements and other information with the SEC. The SEC maintains a website that contains information we file electronically with the SEC, which you can access at http://www.sec.gov.

Our website is located at http://www.westlake.com. Our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other filings with the SEC are available, free of charge, through our website, as soon as reasonably practicable after those reports or filings are electronically filed with or furnished to the SEC. Information on or accessible through our website or any other website is not incorporated by reference in this prospectus supplement or the accompanying prospectus and does not constitute a part of this prospectus supplement or the accompanying prospectus.

This prospectus supplement is part of a registration statement we have filed with the SEC. As permitted by SEC rules, this prospectus supplement does not contain all of the information we have included in the registration statement and the accompanying exhibits and schedules we file with the SEC. You may refer to the registration statement, the exhibits and the schedules for more information about us and our securities. The registration statement, exhibits and schedules are available through the SEC’s website.

We are incorporating by reference information we file with the SEC, which means that we are disclosing important information to you by referring you to those documents. The information we incorporate by reference is an important part of this prospectus supplement and the accompanying prospectus, and later information that we file with the SEC automatically will update and supersede this information. You should not assume that the information in this prospectus supplement is current as of any date other than the date on the front page of this prospectus supplement.

We incorporate by reference the documents listed below and any future filings we make with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this prospectus supplement and until the offering described in this prospectus supplement is completed or is otherwise terminated, in each case excluding any information “furnished” but not “filed,” unless we specifically provide that such “furnished” information is to be incorporated by reference:

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our Annual Report on Form 10-K for the fiscal year ended December 31, 2024, including the portions of our definitive proxy statement on Schedule 14A filed with the SEC on March 28, 2025 that are incorporated by reference therein;

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our Quarterly Reports on Form 10-Q for the quarters ended March 31, 2025, June 30, 2025 and September 30, 2025; and

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our Current Reports on Form 8-K filed with the SEC on March 4, 2025, April 16, 2025, May 12, 2025 and June 17, 2025.

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We will provide a copy of any and all of the information that is incorporated by reference in this prospectus supplement and the accompanying prospectus to any person, including a beneficial owner, to whom this prospectus supplement and the accompanying prospectus is delivered, without charge, upon written or oral request. You may obtain a copy of these filings (other than an exhibit to those filings unless we have specifically incorporated that exhibit by reference into the filing), at no cost, by writing or telephoning us at the following address:

Westlake Corporation

2801 Post Oak Boulevard, Suite 600

Houston, Texas 77056

Attention: Investor Relations

Telephone: (713) 960-9111

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Prospectus

LOGO

Westlake Corporation

Debt Securities

Preferred Stock

Common Stock

Warrants

We may issue and sell from time to time:

•

our debt securities;

•

shares of our common stock;

•

shares of our preferred stock; or

•

warrants to purchase such securities.

TTWF LP, our principal stockholder in which five of our directors have indirect ownership interests, may sell from time to time up to 4,500,000 shares of our common stock.

This prospectus provides you with a general description of the securities that may be offered. We will provide the specific terms of the securities offered in supplements to this prospectus. You should read this prospectus and any applicable prospectus supplement carefully before you invest. Our common stock is listed on the New York Stock Exchange under the symbol “WLK.”

Investing in our securities involves risks. You should carefully consider the risk factors described under “Risk Factors ” beginning on page 3 of this prospectus before you make any investment in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined whether this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is October 31, 2025.

Table of Contents


	Page
ABOUT THIS PROSPECTUS		1
ABOUT WESTLAKE CORPORATION		1
POTENTIAL SUBSIDIARY GUARANTORS		2
RISK FACTORS		3
CAUTIONARY STATEMENTS ABOUT FORWARD-LOOKING STATEMENTS		8
USE OF PROCEEDS		11
DESCRIPTION OF DEBT SECURITIES		12
DESCRIPTION OF CAPITAL STOCK		20
DESCRIPTION OF WARRANTS		26
SELLING STOCKHOLDER		27
PLAN OF DISTRIBUTION		28
LEGAL MATTERS		30
EXPERTS		30
WHERE YOU CAN FIND MORE INFORMATION		30

ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement that we have filed with the Securities and Exchange Commission (the “SEC”) using a “shelf” registration process. Using this process, we may sell any combination of the securities described in this prospectus and the selling stockholder may sell shares of our common stock in one or more offerings. This prospectus provides you with a general description of the securities that may be offered. Each time securities are to be offered pursuant to this prospectus, we will provide a prospectus supplement and, if applicable, a pricing supplement that will describe the specific terms of that offering. The prospectus supplement and any pricing supplement may also add to, update or change the information contained in this prospectus. Please carefully read this prospectus, the prospectus supplement and any pricing supplement together with the information contained in the documents we refer to under the heading “Where You Can Find More Information.”

You should rely only on the information we have provided or incorporated by reference in this prospectus, the prospectus supplement and any pricing supplement. Neither we nor the selling stockholder have authorized any person, including any salesman or broker, to provide you with additional or different information. We and the selling stockholder are not making an offer of these securities in any jurisdiction where the offer is not permitted. You should assume that the information in this prospectus, the accompanying prospectus supplement and any pricing supplement is accurate only as of the date on its cover page and that any information we have incorporated by reference is accurate only as of the date of the document incorporated by reference.

In this prospectus, except under the heading “Description of Debt Securities,” references to “Westlake,” the “Company,” “we,” “us,” and “our” refer to Westlake Corporation and its consolidated subsidiaries, unless the context indicates otherwise.

ABOUT WESTLAKE CORPORATION

We are a vertically integrated global manufacturer and marketer of performance and essential materials and housing and infrastructure products that enhance the lives of people every day. Our products include some of the most widely used materials in the world, which are fundamental to many diverse consumer and industrial markets, including residential construction, flexible and rigid packaging, automotive products, healthcare products, water treatment, wind turbines, coatings as well as other durable and non-durable goods. We operate in two principal operating segments, Performance and Essential Materials and Housing and Infrastructure Products. Performance and Essential Materials includes Westlake North American Vinyls, Westlake North American Chlor-alkali & Derivatives, Westlake European & Asian Chlorovinyls, Westlake Olefins, Westlake Polyethylene and Westlake Epoxy. Housing and Infrastructure Products includes Westlake Royal Building Products, Westlake Pipe & Fittings, Westlake Global Compounds and Westlake Dimex. We are highly integrated along our materials chain with significant downstream integration from ethylene and chlor-alkali (chlorine and caustic soda) into vinyls, polyethylene and styrene monomer. We also have substantial downstream integration from polyvinyl chloride (“PVC”) into our building products, PVC pipes and fittings and PVC compounds in our Housing and Infrastructure Products segment.

We began operations in 1986. Since 1986, we have grown rapidly into an integrated global producer of chemicals and building products. We achieved this growth by acquiring existing plants or constructing new plants and completing numerous capacity or production line expansions. We regularly consider acquisitions and other internal and external growth opportunities that would be consistent with, or complementary to, our overall business strategy.

In 2014, we formed Westlake Chemical Partners LP (“Westlake Partners”) to operate, acquire and develop ethylene production facilities and related assets. Also in 2014, Westlake Partners completed an initial public offering of common units (the “Westlake Partners IPO”). As of the date of this prospectus, Westlake Partners’ assets consisted of a 22.8% limited partner interest in Westlake Chemical OpCo LP (“OpCo”), as well as the

general partner interest in OpCo. Prior to the Westlake Partners IPO, OpCo’s assets were wholly-owned by us. OpCo’s assets include two ethylene production facilities at our olefins facility in Lake Charles, one ethylene production facility at our Calvert City site and a 200-mile common carrier ethylene pipeline that runs from Mont Belvieu, Texas to the Longview, Texas site, which includes our Longview polyethylene production facility. We retain a 77.2% limited partner interest in OpCo, a 40.1% limited partner interest in Westlake Partners (consisting of 14,122,230 common units), a general partner interest in Westlake Partners and incentive distribution rights. The operations of Westlake Partners are consolidated in our financial statements. We are party to certain agreements with Westlake Partners and OpCo whereby, among other things, OpCo sells us 95% of the ethylene it produces on a cost-plus basis that is expected to generate a fixed margin per pound of $0.10. We use this ethylene in the production processes of our Performance and Essential Materials segment.

We are a Delaware corporation with our principal executive offices located at 2801 Post Oak Boulevard, Suite 600, Houston, Texas 77056. Our telephone number at such address is (713) 960-9111.

POTENTIAL SUBSIDIARY GUARANTORS

One or more of our direct or indirect wholly-owned subsidiaries may fully and unconditionally guarantee any series of debt securities offered by this prospectus in the future. We may file one or more post-effective amendments to our registration statement to add such potential subsidiary guarantors. The applicable prospectus supplement will name the subsidiary guarantors, if any, for that series of debt securities and will describe the terms of the guarantee by the subsidiary guarantors.

RISK FACTORS

An investment in our securities involves a high degree of risk. You should carefully consider the risk factors and all of the other information included in, or incorporated by reference into, this prospectus, including those in Item 1A. “Risk Factors” in our Annual Report on Form 10-K for the fiscal year ended December 31, 2024 and in each subsequently filed Quarterly Report on Form 10-Q, in evaluating an investment in our securities. If any of these risks were to occur, our business, financial condition or results of operations could be adversely affected. In that case, the trading price of our common stock or preferred stock or the value of our debt securities could decline, and you could lose all or part of your investment. When we offer and sell any securities pursuant to a prospectus supplement, we may include additional risk factors relevant to such securities in the prospectus supplement.

Risks Related to the Ownership of Our Securities

We will be controlled by our principal stockholder and its affiliates as long as they own a majority of our common stock, and our other stockholders will be unable to affect the outcome of stockholder voting during that time. Our interests may conflict with those of the principal stockholder and its affiliates, and we may not be able to resolve these conflicts on terms possible in arms-length transactions.

As long as TTWF LP (the “principal stockholder” or the “selling stockholder”) and certain of its affiliates (such affiliates, together with the principal stockholder, the “principal stockholder affiliates”), which as of October 27, 2025, beneficially owned approximately 72.4% of our common stock, own a majority of our outstanding common stock, they will be able to exert significant control over us, and our other stockholders, by themselves, will not be able to affect the outcome of any stockholder vote. As a result, the principal stockholder, subject to any fiduciary duty owed to our minority stockholders under Delaware law, will be able to control all matters affecting us (some of which may present conflicts of interest), including:

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the composition of our Board of Directors and, through the Board, any determination with respect to our business direction and policies, including the appointment and removal of officers and the determination of compensation;

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any determinations with respect to mergers or other business combinations or the acquisition or disposition of assets;

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our financing decisions, capital raising activities and the payment of dividends; and

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amendments to our restated certificate of incorporation or second amended and restated bylaws.

The principal stockholder will be permitted to transfer a controlling interest in us without being required to offer our other stockholders the ability to participate or realize a premium for their shares of common stock. A sale of a controlling interest to a third party may adversely affect the market price of our common stock and our business and results of operations because the change in control may result in a change of management decisions and business policy. Because we have elected not to be subject to Section 203 of the General Corporation Law of the State of Delaware, the principal stockholder may find it easier to sell its controlling interest to a third party than if we had not so elected. See “Description of Capital Stock—Delaware Business Combination Statute” for a description of Section 203 and the potential positive and negative consequences, depending on the circumstances, of electing not to be subject to it.

In addition to any conflicts of interest that arise in the foregoing areas, our interests may conflict with those of the principal stockholder affiliates in a number of other areas, including:

•

business opportunities that may be presented to the principal stockholder affiliates and to our officers and directors associated with the principal stockholder affiliates, and competition between the principal stockholder affiliates and us within the same lines of business;

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the solicitation and hiring of employees from each other; and

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agreements with the principal stockholder affiliates relating to corporate services that may be material to our business.

We may not be able to resolve any potential conflicts with the principal stockholder affiliates, and even if we do, the resolution may be less favorable than if we were dealing with an unaffiliated party, particularly if the conflicts are resolved while we are controlled by the principal stockholder affiliates. Our restated certificate of incorporation provides that the principal stockholder affiliates have no duty to refrain from engaging in activities or lines of business similar to ours and that the principal stockholder affiliates will not be liable to us or our stockholders for failing to present specified corporate opportunities to us. See “Description of Capital Stock—Transactions and Corporate Opportunities.”

Public and investor sentiment towards climate change and other sustainability matters could adversely affect our cost of capital and the price of our common stock and preferred stock and the value of our debt securities.

There have been intensifying efforts within the investment community (including investment advisors, investment fund managers, sovereign wealth funds, public pension funds, universities and individual investors) to promote the divestment of, or limit investment in, the stock of companies in the petrochemical industry. There has also been pressure on lenders and other financial services companies to limit or curtail financing of companies in the industry. Because we operate within the petrochemical industry, if these efforts continue or expand, our stock price, the value of our debt securities and our ability to raise capital may be negatively impacted.

Members of the investment community are increasing their focus on sustainability practices and disclosures by public companies, including practices and disclosures related to climate change, as well as D&I initiatives and heightened governance standards. As a result, we may continue to face increasing pressure regarding our sustainability disclosures and practices. Additionally, members of the investment community may screen companies such as ours for sustainability disclosures and performance before investing in our stock. Over the past few years, there has also been an acceleration in investor demand for investing opportunities in sustainability-focused companies, and many large institutional investors have committed to increasing the percentage of their portfolios that are allocated towards investments in companies with a commitment towards sustainability. With respect to any of these investors, our sustainability disclosures and efforts may not satisfy the investor requirements or their requirements may not be made known to us. If we or our securities are unable to meet the sustainability standards or investment criteria set by these investors and funds, we may lose investors or investors may allocate a portion of their capital away from us, our cost of capital may increase, and our stock price may be negatively impacted.

Risks Related to the Common Stock

Substantial sales of our common stock by the principal stockholder or us could cause our stock price to decline and issuances by us may dilute our stockholders’ ownership interest in our company.

We are unable to predict whether significant amounts of our common stock will be sold by the principal stockholder. Any sales of substantial amounts of our common stock in the public market by the principal stockholder or us, or the perception that these sales might occur, could lower the market price of our common stock. Further, if we issue additional equity securities to raise additional capital, our stockholders’ ownership interest in us may be diluted and the value of their investment may be reduced.

The price of our common stock may be volatile.

The market price of our common stock could be subject to significant fluctuations. Among the factors that could affect our stock price are:

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our operating and financial performance and prospects;

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quarterly variations in the rate of growth of our financial indicators, such as earnings per share, net income and revenues;

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changes in revenue or earnings estimates or publication of research reports by analysts;

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speculation in the press or investment community;

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strategic actions by us or our competitors, such as acquisitions or restructurings, and the integration of any acquired businesses;

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sales of shares of our common stock by stockholders;

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actions by institutional investors or by the principal stockholder;

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fluctuations in oil and gas prices;

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the growth rate of the U.S. housing market and the homebuilding industry;

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volatility in the capital and credit markets;

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global competition and the effects of trade barriers, tariffs and duties;

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general market conditions, including fluctuations in feedstock, energy and commodity prices;

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the impact and effects of public health crises, pandemics and epidemics; and

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U.S. and international economic, legal and regulatory factors unrelated to our performance.

The stock markets in general have experienced extreme volatility in recent years that has at times been unrelated to the operating performance of particular companies. These broad market fluctuations may adversely affect the trading price of our common stock and, as a result, an investment in our common stock.

If we are unable to pay regular dividends on our common stock, our stockholders may not receive funds without selling their common stock.

Shortly following our initial public offering in 2004, we paid our initial regular quarterly dividend of at least $0.02125 per share. We have paid regular quarterly dividends since our initial dividend. On August 8, 2025, our Board of Directors declared a dividend of $0.53 per share payable on September 4, 2025 to our stockholders of record as of the close of business on August 19, 2025. Any payment of future dividends will be at the discretion of our Board of Directors and will depend on, among other things, our earnings, financial condition, capital requirements, level of indebtedness, statutory and contractual restrictions applying to the payment of dividends, and other considerations that our Board of Directors deems relevant. In addition, our future debt agreements could include restrictions on the payment of dividends. To the extent that we are restricted from paying dividends, our stockholders may have to sell some or all of their common stock in order to generate cash flow from their investment. Our stockholders may not receive a gain on their investment when they sell their common stock and they may lose the entire amount of the investment.

Provisions in our charter documents or Delaware law may inhibit a takeover, which could adversely affect the value of our common stock.

Our restated certificate of incorporation and second amended and restated bylaws, as well as Delaware corporate law, contain provisions that could delay or prevent a change of control or changes in our management that a stockholder might consider favorable. These provisions apply even if the offer may be considered beneficial by some of our stockholders. If a change of control or change in management is delayed or prevented, the market price of our common stock could decline. Please read “Description of Capital Stock” for a description of these provisions.

Risks Related to the Debt Securities

Our holding company structure may affect our ability to make payments on our debt securities. Holders of our debt securities may be structurally subordinated to the creditors of our subsidiaries.

We currently conduct our operations through subsidiaries, and our operating income and cash flows are generated by our subsidiaries. As a result, cash we obtain from our subsidiaries is the principal source of funds necessary to meet our debt service obligations. Contractual provisions or laws, as well as our subsidiaries’ financial condition and operating requirements, may limit our ability to obtain cash from our subsidiaries that we require to pay our debt service obligations, including payments on the debt securities. In addition, holders of the debt securities will have a junior position to the claims of creditors, including trade creditors and tort claimants, of our subsidiaries to the extent that such subsidiaries do not guarantee such debt securities. In the event of a bankruptcy, liquidation or reorganization of any of our non-guarantor subsidiaries, holders of that subsidiary’s indebtedness and its trade creditors will generally be entitled to payment of their claims from the assets of the subsidiary before any assets are made available for distribution to us.

A holder’s right to receive payments on the debt securities is effectively subordinated to the rights of our existing and future secured creditors to the extent of their collateral. Further, the guarantees of the debt securities by the subsidiary guarantors, if any, are effectively subordinated to the subsidiary guarantors’ existing and future secured indebtedness.

Holders of our secured indebtedness and the secured indebtedness of the subsidiary guarantors, if any, will have claims that are prior to the claims of holders of the debt securities to the extent of the value of the assets securing that other indebtedness. In the event of any distribution or payment of our assets in any foreclosure, dissolution, winding-up, liquidation, reorganization or other bankruptcy proceeding, holders of secured indebtedness will have prior claim to our assets that constitute their collateral. Holders of the debt securities will participate ratably with all holders of our unsecured and unsubordinated indebtedness, and potentially with all of our other general creditors, based upon the respective amounts owed to each holder or creditor, in our remaining assets. We may apply proceeds of certain asset sales to reduce our secured indebtedness or other secured obligations, but such application will not permanently reduce our ability to incur secured indebtedness and other secured obligations under the indenture in the future. In any of the foregoing events, we cannot assure you that there will be sufficient assets to pay amounts due on the debt securities. As a result, holders of the debt securities may receive less, ratably, than holders of secured indebtedness.

A holder’s right to receive payments on the debt securities could be adversely affected if any of our non-guarantor subsidiaries declares bankruptcy, liquidates or reorganizes.

Some but not all of our subsidiaries may guarantee the debt securities. In the event of a bankruptcy, liquidation or reorganization of any of our non-guarantor subsidiaries, holders of that subsidiary’s indebtedness and its trade creditors will generally be entitled to payment of their claims from the assets of the subsidiary before any assets are made available for distribution to us.

Federal and state statutes allow courts, under specific circumstances, to void guarantees and require holders of the debt securities to return payments received from guarantors.

Under the federal bankruptcy law and comparable provisions of state fraudulent transfer laws, a guarantee could be voided or claims in respect of a guarantee could be subordinated to all other debts of the applicable guarantor if, among other things, the guarantor, at the time it incurred the indebtedness evidenced by its guarantee, received less than reasonably equivalent value or fair consideration for the incurrence of such guarantee and either:

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was insolvent or rendered insolvent by reason of such incurrence;

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was engaged or about to engage in a business or transaction for which the guarantor’s remaining assets constituted unreasonably small capital; or

•

intended to incur, or believed that it would incur, debts beyond its ability to pay such debts as they mature.

In addition, any payment by that guarantor pursuant to its guarantee could be voided and required to be returned to the guarantor or to a fund for the benefit of the creditors of the guarantor.

The measures of insolvency for purposes of these fraudulent transfer laws will vary depending upon the law applied in any proceeding to determine whether a fraudulent transfer has occurred. Generally, a guarantor would be considered insolvent if, at the relevant time, the sum of its debts and other liabilities, including contingent liabilities, was greater than the sum of its assets at a fair valuation, and a guarantor that was generally not then paying its debts as they became due would be presumed to be insolvent.

We may incur additional debt ranking equal to the debt securities.

If we incur any additional debt that ranks equally with the debt securities, the holders of that debt will be entitled to share ratably with the holders of the debt securities in any proceeds distributed in connection with any insolvency, liquidation, reorganization, dissolution or other winding-up of our company. This may have the effect of reducing the amount of proceeds paid to a holder of debt securities.

CAUTIONARY STATEMENTS ABOUT FORWARD-LOOKING STATEMENTS

The Private Securities Litigation Reform Act of 1995 provides safe harbor provisions for forward-looking information. Certain of the statements contained in this prospectus are forward-looking statements. All statements, other than statements of historical facts, included in this prospectus that address activities, events or developments that we expect, project, believe or anticipate will or may occur in the future are forward-looking statements. Forward-looking statements can be identified by the use of words such as “believes,” “intends,” “may,” “should,” “could,” “anticipates,” “expected” or comparable terminology, or by discussions of strategies or trends. Although we believe that the expectations reflected in such forward-looking statements are reasonable, we cannot give any assurances that these expectations will prove to be correct. Forward-looking statements relate to matters such as:

•

recoverability of the carrying value of our long-lived assets, including tangible assets and intangible assets with finite lives, and the fair value of our reporting units with goodwill;

•

future operating rates, margins, cash flows and demand for our products;

•

industry market outlook, including the price of crude oil, natural gas, ethane, housing starts and repair and remodeling activity;

•

macroeconomic outlook, including elevated interest rates, inflation and possible recession;

•

widespread outbreak of an illness or any other communicable disease, or any other public health crisis;

•

production capacities;

•

the impact of ongoing conflicts in the Middle East and between Russia and Ukraine;

•

currency devaluation;

•

our ability to borrow under our credit agreement;

•

our ability to meet our liquidity needs;

•

our ability to meet debt obligations under our debt instruments;

•

our intended quarterly dividends;

•

future capacity additions and expansions in the industries in which we compete;

•

timing, funding and results of capital projects;

•

pension plan obligations, funding requirements and investment policies;

•

recovery of losses under our insurance policies;

•

effects of pending legal proceedings and settlements;

•

timing of and amount of capital expenditures;

•

increased costs and other effects of tariffs imposed by the U.S. government, and any effects on trading relationships among the United States and other countries; and

•

We have based these statements on assumptions and analyses in light of our experience and perception of historical trends, current conditions, expected future developments and other factors we believe were appropriate in the circumstances when the statements were made. Forward-looking statements by their nature involve substantial risks and uncertainties that could significantly impact expected results, and actual future results could differ materially from those described in such statements. While it is not possible to identify all factors, we continue to face many risks and uncertainties. Among the factors that could cause actual future results to differ materially are the risks and uncertainties discussed under “Risk Factors” in this prospectus and in the section entitled “Risk Factors” in our most recent Annual Report on Form 10-K and those described from time to time in our other filings with the SEC including, but not limited to, the following:

•

general economic and business conditions, including inflation, interest rates and possible recession;

•

the cyclical nature of the chemical and building products industries;

•

the availability, cost and volatility of raw materials and energy;

•

uncertainties associated with the United States, European and worldwide economies, including those due to political tensions and conflict in the Middle East, Russia and Ukraine and elsewhere;

•

uncertainties associated with pandemic infectious diseases;

•

uncertainties associated with climate change;

•

the potential impact on demand for ethylene, polyethylene and polyvinyl chloride due to initiatives such as recycling and customers seeking alternatives to polymers;

•

current and potential governmental regulatory actions in the United States and other countries;

•

industry production capacity and operating rates;

•

the supply/demand balance for our products;

•

competitive products and pricing pressures;

•

instability in the credit and financial markets;

•

access to capital markets;

•

terrorist acts;

•

changes in laws or regulations, including trade policies and tariffs imposed on or by foreign jurisdictions;

•

the effects of government shutdowns;

•

technological developments;

•

information systems failures and cyberattacks;

•

foreign currency exchange risks;

•

our ability to implement our business strategies; and

•

creditworthiness of our customers.

Many of these factors are beyond our ability to control or predict. Any of these factors, or a combination of these factors, could materially affect our future results of operations and the ultimate accuracy of the forward-looking statements. These forward-looking statements are not guarantees of our future performance, and our actual results and future developments may differ materially from those projected in the forward-looking statements. Management cautions against putting undue reliance on forward-looking statements or projecting any future results based on such statements or present or prior earnings levels. Every forward-looking statement speaks only as of the date of the particular statement, and we undertake no obligation to publicly update or revise any forward-looking statements.

USE OF PROCEEDS

Unless we inform you otherwise in the applicable prospectus supplement, we expect to use the net proceeds from the sale of securities for general corporate purposes. These purposes may include:

•

repayment or refinancing of debt;

•

acquisitions;

•

working capital;

•

capital expenditures; and

•

repurchases and redemptions of securities.

Pending any specific application, we may initially invest funds in short-term investments or apply them to the reduction of short-term indebtedness.

We will not receive any proceeds from the sale of any shares of our common stock that may be sold by the selling stockholder.

DESCRIPTION OF DEBT SECURITIES

The debt securities covered by this prospectus will be our general unsecured obligations. We will issue debt securities under the indenture dated as of January 1, 2006, as amended or supplemented from time to time, by and among us, the subsidiary guarantors party thereto and The Bank of New York Mellon Trust Company, N.A. (as successor to JPMorgan Chase Bank, National Association), as trustee.

We have summarized material provisions of the indenture and the debt securities below. This summary is not complete. We have filed the indenture with the SEC as an exhibit to the registration statement, and you should read the indenture for provisions that may be important to you. Please read “Where You Can Find More Information.”

In this summary description of the debt securities, unless we state otherwise, or the context clearly indicates otherwise, all references to “we,” “us,” or “our” refer to Westlake Corporation only and not to any of its subsidiaries.

General

The indenture does not limit the amount of debt securities that may be issued under it, and does not limit the amount of other unsecured debt securities that we may issue. We may issue debt securities under the indenture from time to time in one or more series. As of September 30, 2025, $3,900 million and €700 million of debt securities were outstanding under the indenture, which includes $750 million of 3.60% senior notes due 2026, $300 million of 3.375% senior notes due 2030, $250 million of 3.50% senior notes due 2032, $350 million of 2.875% senior notes due 2041, $700 million of 5.00% senior notes due 2046, $500 million of 4.375% senior notes due 2047, $600 million of 3.125% senior notes due 2051 and $450 million of 3.375% senior notes due 2061 (collectively, the “U.S. Dollar Senior Notes”), as well as €700 million of 1.625% senior notes due 2029.

We are not obligated to issue all debt securities of one series at the same time and, unless otherwise provided in the applicable prospectus supplement, we may reopen a series, without giving notice to or seeking the consent of the holders of the debt securities of that series, for the issuance of additional debt securities of that series. Additional debt securities of a particular series will have the same terms and conditions as outstanding debt securities of such series, except for the date of original issuance and the offering price and, if applicable, the initial interest payment date and initial interest accrual date, and will be consolidated with, and form a single series with, such outstanding debt securities.

The debt securities will rank equally in right of payment with all of our other unsecured and unsubordinated debt and senior in right of payment to all of our subordinated indebtedness, if any. The debt securities will be effectively subordinated to, and thus have a junior position to, our secured indebtedness with respect to the assets securing that indebtedness.

The indenture does not contain any covenants or other provisions designed to protect holders of the debt securities in the event we participate in a highly leveraged transaction or upon a change of control. The indenture also does not contain provisions that give holders of the debt securities the right to require us to repurchase their securities in the event of a decline in our credit rating for any reason, including as a result of a takeover, recapitalization or similar restructuring or otherwise.

Ranking

In the event of any distribution or payment of our assets in any foreclosure, dissolution, winding-up, liquidation, reorganization or other bankruptcy proceeding, holders of secured indebtedness will have prior claim to our assets that constitute their collateral. Holders of the debt securities will participate ratably with all holders of our unsecured and unsubordinated indebtedness, and potentially with all of our other general creditors, based upon the respective amounts owed to each holder or creditor, in our remaining assets. See “Risk Factors—Risks Related to the Debt Securities—A holder’s right to receive payments on the debt securities is effectively subordinated to the rights of our existing and future secured creditors to the extent of their collateral. Further, the guarantees of the debt securities by the subsidiary guarantors, if any, are effectively subordinated to the subsidiary guarantors’ existing and future secured indebtedness.”

The debt securities will rank equally with all of our other unsecured and unsubordinated indebtedness. As of September 30, 2025, we had an aggregate of $3,914 million and €700 million of unsecured and unsubordinated indebtedness, consisting of $3,900 million aggregate principal amount of U.S. Dollar Senior Notes as well as €700 million of 1.625% senior notes due 2029 that rank equally with the other series of unsecured and unsubordinated debt securities issued under the indenture. If debt securities are guaranteed, the guarantees will rank equally with all of the subsidiary guarantors’ other unsecured and unsubordinated debt from time to time outstanding and senior to any subordinated debt of the subsidiary guarantors, if any.

If debt securities are not guaranteed by any of the subsidiary guarantors, then the debt securities will be structurally subordinated to the existing and future obligations of our subsidiaries. As of September 30, 2025, our subsidiaries had an aggregate of $12 million of outstanding long-term indebtedness.

Terms

The prospectus supplement relating to any series of debt securities being offered will include specific terms relating to the offering. These terms will include some or all of the following:

•

the title of the debt securities;

•

the total principal amount of the debt securities;

•

whether we will issue the debt securities in individual certificates to each holder or in the form of temporary or permanent global securities held by a depositary on behalf of holders;

•

the date or dates on which the principal of and any premium on the debt securities will be payable;

•

any interest rate, the date from which interest will accrue, interest payment dates and record dates for interest payments;

•

whether and under what circumstances we will pay any additional amounts with respect to the debt securities;

•

whether debt securities are entitled to any guarantee of any subsidiary guarantors and the identity of any such subsidiary guarantors for that series and the terms of such guarantee;

•

the place or places where payments on the debt securities will be payable;

•

any provisions for optional redemption or early repayment;

•

any sinking fund or other provisions that would obligate us to redeem, purchase or repay the debt securities;

•

the denominations in which we will issue the debt securities if other than $1,000 and integral multiples of $1,000;

•

whether payments on the debt securities will be payable in foreign currency or currency unit or another form and whether payments will be payable by reference to any index or formula;

•

the portion of the principal amount of the debt securities that will be payable if the maturity is accelerated, if other than the entire principal amount;

•

any additional means of defeasance of the debt securities, any additional conditions or limitations to defeasance of the debt securities or any changes to those conditions or limitations;

•

any changes or additions to the events of default or covenants described in this prospectus;

•

any restrictions or other provisions relating to the transfer or exchange of the debt securities;

•

any terms for the conversion or exchange of the debt securities for other securities; and

•

any other terms of the debt securities not inconsistent with the indenture.

We may sell the debt securities at a discount, which may be substantial, below their stated principal amount. These debt securities may bear no interest or interest at a rate that at the time of issuance is below market rates. If we sell these debt securities, we will describe in the prospectus supplement any material United States federal income tax consequences and other special considerations.

If we sell any of the debt securities for any foreign currency or currency unit or if payments on the debt securities are payable in any foreign currency or currency unit, we will describe in the applicable prospectus supplement the restrictions, elections, tax consequences, specific terms and other information relating to those debt securities and the foreign currency or currency unit.

Guarantees

Consolidation, Merger and Sales of Assets

The indenture generally permits a consolidation or merger involving us. It also permits us to sell, lease, convey, assign, transfer or otherwise dispose of all or substantially all of our assets. We have agreed, however, that we will not consolidate with or merge into any entity or sell, lease, convey, assign, transfer or dispose of all or substantially all of our assets to any entity unless:

(1)

either

•

we are the continuing entity; or

•

the resulting entity is organized under the laws of the United States, any state thereof or the District of Columbia, and expressly assumes by supplemental indenture the due and punctual payment of the principal of, premium (if any) and interest on and any additional amounts with respect to the debt securities and the performance of our covenants and obligations under the indenture and the debt securities; and

(2)	immediately after giving effect to the transaction or series of transactions, no default or event of default under the indenture has occurred and is continuing or would result from the transaction(s).

This covenant will not apply to any merger of another entity into us. Upon any transaction of the type described in and effected in accordance with this section, the resulting entity will succeed to and be substituted for and may exercise all of our rights and powers under the indenture and the debt securities with the same effect as if the resulting entity had been named as us in the indenture. In the case of any asset transfer or disposition other than a lease, when the resulting entity assumes all of our obligations and covenants under the indenture and the debt securities, we will be relieved of all such obligations.

Events of Default

Unless we inform you otherwise in the applicable prospectus supplement, the following are events of default with respect to a series of debt securities:

•

our failure to pay interest on any debt security of that series for 30 days when due;

•

our failure to pay principal of or any premium on any debt security of that series when due;

•

our failure to deposit any sinking fund payment relating to any debt security of that series for 30 days when due;

•

our failure to comply with any covenant or agreement in that series of debt securities or the indenture (other than an agreement or covenant that has been included in the indenture solely for the benefit of other series of debt securities) for 60 days after receipt of written notice by the trustee or by the holders of at least 25% in principal amount of the outstanding debt securities issued under the indenture that are affected by that failure;

•

specified events involving bankruptcy, insolvency or reorganization;

•

if applicable, specified events involving the guarantees; and

•

any other event of default provided for that series of debt securities.

A default under one series of debt securities will not necessarily be a default under any other series. If a default or event of default for any series of debt securities occurs, is continuing and is known to the trustee, the trustee will notify the holders of applicable debt securities within 90 days after it occurs. The trustee may withhold notice to the holders of the debt securities of any default or event of default, except in any payment on the debt securities, if the trustee in good faith determines that withholding notice is in the interests of the holders of those debt securities.

If an event of default for any series of debt securities occurs and is continuing, other than in specific events involving bankruptcy, insolvency or reorganization, the trustee or the holders of at least 25% in principal amount of the outstanding debt securities of the series affected by the default (or, in some cases, 25% in principal amount of all debt securities issued under the indenture that are affected, voting as one class) may declare the principal of and all accrued and unpaid interest on those debt securities to be due and payable immediately. If an event of default relating to certain events of bankruptcy, insolvency or reorganization occurs, the principal of and accrued and unpaid interest on all the debt securities of that series will become immediately due and payable without any action on the part of the trustee or any holder. At any time after a declaration of acceleration has been made, the holders of a majority in principal amount of the outstanding debt securities of the series affected by the default (or, in some cases, a majority in principal amount of all debt securities issued under the indenture that are affected, voting as one class) may in some cases rescind this accelerated payment requirement and its consequences.

A holder of a debt security of any series issued under the indenture may pursue any remedy under the indenture only if:

•

the holder gives the trustee written notice of a continuing event of default with respect to that series of debt securities;

•

the holders of at least 25% in principal amount of the outstanding debt securities of that series make a written request to the trustee to pursue the remedy;

•

the holders offer to the trustee indemnity satisfactory to the trustee against any loss, liability or expense;

•

the trustee does not comply with the request within 60 days after receipt of the request and offer of indemnity; and

•

during that 60-day period, the holders of a majority in principal amount of the debt securities of that series do not give the trustee a direction inconsistent with the request.

This provision does not, however, affect the right of a holder of a debt security to sue for enforcement of any overdue payment.

In most cases, the trustee will be under no obligation to exercise any of its rights or powers under the indenture at the request or direction of any of the holders unless those holders have offered to the trustee indemnity satisfactory to it. Subject to this provision for indemnification, the holders of a majority in principal amount of the outstanding debt securities of a series (or of all debt securities issued under the indenture that are affected, voting as one class) generally may direct the time, method and place of:

•

conducting any proceeding for any remedy available to the trustee; or

•

exercising any trust or power conferred on the trustee relating to or arising as a result of an event of default.

If an event of default occurs and is continuing, the trustee will be required to use the degree of care and skill of a prudent person in the conduct of such person’s own affairs.

The indenture requires us to furnish to the trustee annually a statement as to our performance of certain of our obligations under the indenture and as to any default in performance.

Modification and Waiver

We and the trustee may supplement or amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding debt securities of all series issued under the indenture that are affected by the amendment or supplement (voting as one class). Without the consent of the holder of each debt security affected, however, no modification may:

•

reduce the amount of debt securities whose holders must consent to an amendment, supplement or waiver;

•

reduce the rate of or change the time for payment of interest on the debt security;

•

reduce the principal of, any premium on or any mandatory sinking fund payment with respect to, the debt security or change its stated maturity;

•

reduce any premium payable on the redemption of the debt security or change the time at which the debt security may or must be redeemed;

•

change any obligation to pay additional amounts on the debt security;

•

make payments on the debt security payable in currency other than as originally stated in the debt security;

•

impair the holder’s right to institute suit for the enforcement of any payment on or with respect to the debt security;

•

make any change in the percentage of principal amount of debt securities necessary to waive compliance with certain provisions of the indenture or to make any change in the provision related to modification;

•

waive a continuing default or event of default regarding any payment on the debt securities; or

•

if applicable, make any change that materially and adversely affects the right to convert any debt security.

We and the trustee may supplement or amend the indenture or waive any provision of the indenture without the consent of any holders of debt securities issued under the indenture in certain circumstances, including:

•

to cure any ambiguity, omission, defect or inconsistency;

•

to provide for the assumption of our obligations under the indenture by a successor upon any merger, consolidation or asset transfer permitted under the indenture;

•

to provide for uncertificated debt securities in addition to or in place of certificated debt securities or to provide for bearer debt securities;

•

to provide any security for, or to add any guarantees of or obligors on, any series of debt securities;

•

to comply with any requirement to effect or maintain the qualification of the indenture under the Trust Indenture Act of 1939, as amended;

•

to add covenants that would benefit the holders of any debt securities or to surrender any rights we have under the indenture;

•

to add events of default with respect to any series of debt securities;

•

to make any change that does not adversely affect any outstanding debt securities of any series issued under the indenture in any material respect;

•

to establish the form or terms of any debt securities and to accept the appointment of a successor trustee, each as permitted under the indenture;

•

to supplement any of the provisions of the indenture to the extent necessary to permit or facilitate the defeasance and discharge of any series of debt securities; and

•

to evidence and provide for the appointment of a successor trustee or to provide for or facilitate the administration of the trusts under the indenture by more than one trustee.

The holders of a majority in principal amount of the outstanding debt securities of any series (or, in some cases, a majority in principal amount of all debt securities issued under the indenture that are affected, voting as one class) may waive any existing or past default or event of default with respect to those debt securities. Those holders may not, however, waive any default or event of default in any payment on any debt security or compliance with a provision that cannot be amended or supplemented without the consent of each holder affected.

Defeasance and Discharge

Defeasance. When we use the term defeasance, we mean discharge from some or all of our obligations under the indenture. If we deposit with the trustee under the indenture any combination of money or government securities sufficient to make payments on the debt securities of a series issued under the indenture on the dates those payments are due, then, at our option, either of the following will occur:

•

we will be discharged from our obligations with respect to the debt securities of that series (“legal defeasance”); or

•

we will no longer have any obligation to comply with specified restrictive covenants with respect to the debt securities of that series, the covenant described under “—Consolidation, Merger and Sales of Assets” and other specified covenants under the indenture, and the related events of default will no longer apply (“covenant defeasance”).

If a series of debt securities is defeased, the holders of the debt securities of that series will not be entitled to the benefits of the indenture, except for obligations to register the transfer or exchange of debt securities, replace stolen, lost or mutilated debt securities or maintain paying agencies and hold money for payment in trust. In the case of covenant defeasance, our obligation to pay principal, premium and interest on the debt securities, will also survive.

Unless we inform you otherwise in the applicable prospectus supplement, we will be required to deliver to the trustee an opinion of counsel that the deposit and related defeasance would not cause the holders of the debt securities to recognize income, gain or loss for U.S. federal income tax purposes and that the holders would be subject to U.S. federal income tax on the same amounts, in the same manner and at the same times as would have

been the case if the deposit and related defeasance had not occurred. If we elect legal defeasance, that opinion of counsel must be based upon a ruling from the United States Internal Revenue Service or a change in law to that effect.

Under current U.S. federal income tax law, legal defeasance would likely be treated as a taxable exchange of debt securities to be defeased for interests in the defeasance trust. As a consequence, a United States holder would recognize gain or loss equal to the difference between the holder’s cost or other tax basis for the debt securities and the value of the holder’s interest in the defeasance trust, and thereafter would be required to include in income a share of the income, gain or loss of the defeasance trust. Under current U.S. federal income tax law, covenant defeasance would not be treated as a taxable exchange of such debt securities.

Satisfaction and Discharge. In addition, the indenture will cease to be of further effect with respect to the debt securities of a series issued under the indenture, subject to exceptions relating to compensation and indemnity of the trustee under the indenture and repayment to us of excess money or government securities, when:

•

either

•

all outstanding debt securities of that series have been delivered to the trustee for cancellation; or

•

all outstanding debt securities of that series not delivered to the trustee for cancellation either:

•

have become due and payable;

•

will become due and payable at their stated maturity within one year; or

•

are to be called for redemption within one year; and

•

we have deposited with the trustee any combination of money or government securities in trust sufficient to pay the entire indebtedness on the debt securities of that series when due; and

•

we have paid all other sums payable by us with respect to the debt securities of that series.

Governing Law

New York law will govern the indenture, the debt securities and the guarantees, if any.

The Trustee

The Bank of New York Mellon Trust Company, N.A. (successor to JPMorgan Chase Bank, National Association) acts as the trustee under the indenture. Unless we inform you otherwise in a prospectus supplement, The Bank of New York Mellon Trust Company, N.A. will act as the trustee with respect to the debt securities described in such prospectus supplement.

The indenture contains limitations on the right of the trustee, if it or any of its affiliates is then our creditor or, if applicable, a creditor of a subsidiary guarantor, if any, to obtain payment of claims or to realize on certain property received for any such claim, as security or otherwise. The trustee and its affiliates are permitted to engage in other transactions with us, and if applicable, the subsidiary guarantors. If, however, the trustee acquires any conflicting interest, it must eliminate that conflict or resign within 90 days after ascertaining that it has a conflicting interest and after the occurrence of a default under the indenture, unless the default has been cured, waived or otherwise eliminated within the 90-day period.

Payments and Paying Agents

Unless we inform you otherwise in the applicable prospectus supplement, we will make payments on the debt securities in U.S. dollars at the office of the trustee and any paying agent. At our option, however, payments may be made by wire transfer for global debt securities or by check mailed to the address of the person entitled to

the payment as it appears in the security register. Unless we inform you otherwise in the applicable prospectus supplement, we will make interest payments to the person in whose name the debt security is registered at the close of business on the record date for the interest payment.

Unless we inform you otherwise in the applicable prospectus supplement, the trustee under the indenture will be designated as the paying agent for payments on debt securities issued under the indenture. We may at any time designate additional paying agents or rescind the designation of any paying agent or approve a change in the office through which any paying agent acts.

If the principal of or any premium or interest on debt securities of a series is payable on a day that is not a business day, the payment will be made on the following business day. For these purposes, unless we inform you otherwise in the applicable prospectus supplement, a “business day” is any day that is not a Saturday, a Sunday or a day on which banking institutions in any of New York, New York, Houston, Texas or a place of payment on the debt securities of that series is authorized or obligated by law, regulation or executive order to remain closed.

Subject to the requirements of any applicable abandoned property laws, the trustee and paying agent will pay to us upon written request any money held by them for payments on the debt securities that remains unclaimed for two years after the date upon which that payment has become due. After payment to us, holders entitled to the money must look to us for payment. In that case, all liability of the trustee or paying agent with respect to that money will cease.

Form, Exchange, Registration and Transfer

We will issue the debt securities in registered form, without interest coupons. Debt securities of any series will be exchangeable for other debt securities of the same series, the same total principal amount and the same terms but in different authorized denominations in accordance with the indenture. Holders may present debt securities for registration of transfer at the office of the security registrar or any transfer agent designated by us. The security registrar or transfer agent will effect the transfer or exchange if its requirements and the requirements of the indenture are met. We will not charge a service charge for any registration of transfer or exchange of the debt securities. We may, however, require payment of any transfer tax or similar governmental charge payable for that registration.

We will appoint the trustee as security registrar for the debt securities. If the applicable prospectus supplement refers to any transfer agents we initially designate, we may at any time rescind that designation or approve a change in the location through which any transfer agent acts. We are required to maintain an office or agency for transfers and exchanges in each place of payment. We may at any time designate additional transfer agents for any series of debt securities.

In the case of any redemption of debt securities of a series or any repurchase of debt securities of a series required under the terms of the series, we will not be required to register the transfer or exchange of:

•

any debt security of that series during a period beginning 15 business days prior to the mailing of the relevant notice of redemption or repurchase and ending on the close of business on the day of mailing of such notice; or

•

any debt security of that series that has been called for redemption in whole or in part, except the unredeemed portion of any debt security being redeemed in part.

Book-Entry Debt Securities

We may issue the debt securities of a series in the form of one or more global debt securities that would be deposited with a depositary or its nominee identified in the applicable prospectus supplement. We may issue global debt securities in either temporary or permanent form. We will describe in the applicable prospectus supplement the terms of any depositary arrangement and the rights and limitations of owners of beneficial interests in any global debt security.

DESCRIPTION OF CAPITAL STOCK

General

The following descriptions are summaries of material terms of our common stock, preferred stock, restated certificate of incorporation and second amended and restated bylaws. Copies of our restated certificate of incorporation and second amended and restated bylaws have been incorporated by reference as exhibits to the registration statement of which this prospectus is a part, and you are urged to review these documents. Please read “Where You Can Find More Information.”

As of the date of this prospectus, our authorized capital stock consists of 300 million shares of common stock, par value $0.01 per share, and 50 million shares of preferred stock, par value $0.01 per share.

Common Stock

Each share of common stock entitles the holder to one vote on all matters on which holders are permitted to vote, including the election of directors. There are no cumulative voting rights. Accordingly, holders of a majority of the total votes entitled to vote in an election of directors will be able to elect all of the directors standing for election. Subject to preferences that may be applicable to any outstanding preferred stock, the holders of the common stock will share equally on a per share basis any dividends when, as and if declared by the Board of Directors out of funds legally available for that purpose. If we are liquidated, dissolved or wound up, the holders of our common stock will be entitled to a ratable share of any distribution to stockholders, after satisfaction of all of our liabilities and of the prior rights of any outstanding class of our preferred stock. Our common stock has no preemptive or conversion rights or other subscription rights. There are no redemption or sinking fund provisions applicable to our common stock. All outstanding shares of our common stock are fully paid and nonassessable.

Preferred Stock

Our Board of Directors has the authority, without stockholder approval, to issue shares of preferred stock from time to time in one or more series, and to fix the number of shares and terms of each such series. The Board may determine the designation and other terms of each series, including the following:

•

dividend rates;

•

whether dividends will be cumulative or non-cumulative;

•

redemption rights;

•

liquidation rights;

•

sinking fund provisions;

•

conversion or exchange rights; and

•

voting rights.

The issuance of preferred stock, while providing us with flexibility in connection with possible acquisitions and other transactions, could adversely affect the voting power of holders of our common stock. It could also affect the likelihood that holders of our common stock will receive dividend payments and payments upon liquidation.

The issuance of shares of preferred stock, or the issuance of rights to purchase shares of preferred stock, could be used to discourage an attempt to obtain control of our company. For example, if, in the exercise of its fiduciary obligations, our Board of Directors were to determine that a takeover proposal was not in the best interest of our stockholders, the Board could authorize the issuance of a series of preferred stock containing class

voting rights that would enable the holder or holders of this series to prevent a change of control transaction or make it more difficult. Alternatively, a change of control transaction deemed by the Board to be in the best interest of our stockholders could be facilitated by issuing a series of preferred stock having sufficient voting rights to provide a required percentage vote of the stockholders.

The prospectus supplement relating to any series of preferred stock that we may offer will include specific terms relating to the offering. In connection with any offering of shares of preferred stock, we will file a form of certificate of designation with the SEC, and you should read the certificate of designation for provisions that may be important to you. The applicable prospectus supplement will summarize the general terms of any such series of preferred stock.

Charter and Bylaw Provisions

Election and Removal of Directors

Our Board of Directors consists of between one and 15 directors, excluding any directors elected by holders of preferred stock pursuant to provisions applicable in the case of defaults. The exact number of directors will be fixed from time to time by resolution of the Board. Our Board of Directors is divided into three classes serving staggered three-year terms, with only one class being elected each year by our stockholders. At each annual meeting of stockholders, directors will be elected to succeed the class of directors whose terms have expired. This system of electing and removing directors may discourage a third party from making a tender offer or otherwise attempting to obtain control of us, because it generally makes it more difficult for stockholders to replace a majority of the directors. In addition, no director may be removed except for cause, and directors may be removed for cause by an affirmative vote of shares representing a majority of the shares then entitled to vote at an election of directors. Any vacancy occurring on the Board of Directors and any newly created directorship may only be filled by the affirmative vote of a majority of the remaining directors in office.

Stockholder Meetings

Our restated certificate of incorporation and our second amended and restated bylaws provide that special meetings of our stockholders may be called only by the chairman of our Board of Directors or a majority of the directors. Our restated certificate of incorporation and our second amended and restated bylaws specifically deny any power of any other person to call a special meeting.

Stockholder Action by Written Consent

Our restated certificate of incorporation and our second amended and restated bylaws provide that holders of our common stock will not be able to act by written consent without a meeting, unless such consent is unanimous.

Amendment of Certificate of Incorporation

The provisions of our restated certificate of incorporation described above under “—Election and Removal of Directors,” “—Stockholder Meetings” and “—Stockholder Action by Written Consent” may be amended only by the affirmative vote of holders of at least 75% of the voting power of our outstanding shares of voting stock, voting together as a single class. The affirmative vote of holders of at least a majority of the voting power of our outstanding shares of voting stock is generally required to amend other provisions of our restated certificate of incorporation.

Amendment of Bylaws

Our second amended and restated bylaws may generally be altered, amended or repealed, and new bylaws may be adopted, with:

•

the affirmative vote of a majority of directors present at any regular or special meeting of the Board of Directors called for that purpose, provided that any alteration, amendment or repeal of, or adoption of

any bylaw inconsistent with specified provisions of the bylaws, including those related to special and annual meetings of stockholders, action of stockholders by written consent, classification of the Board of Directors, nomination of directors, special meetings of directors, removal of directors, committees of the Board of Directors and indemnification of directors and officers, requires the affirmative vote of at least 75% of all directors in office at a meeting called for that purpose; or

•

the affirmative vote of holders of 75% of the voting power of our outstanding shares of voting stock, voting together as a single class.

Other Limitations on Stockholder Actions

Our second amended and restated bylaws also impose some procedural requirements on stockholders who wish to:

•

make nominations in the election of directors;

•

propose that a director be removed;

•

propose any repeal or change in our bylaws; or

•

propose any other business to be brought before an annual or special meeting of stockholders.

Under these procedural requirements, in order to bring a proposal before a meeting of stockholders, a stockholder must deliver timely notice of a proposal pertaining to a proper subject for presentation at the meeting to our corporate secretary along with the following:

•

a description of the business or nomination to be brought before the meeting and the reasons for conducting such business at the meeting;

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the stockholder’s name and address;

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the number of shares of our stock beneficially owned by the stockholder and evidence of such ownership; and

•

the names and addresses of all persons with whom the stockholder is acting in concert and a description of all arrangements and understandings with those persons, and the number of shares of our stock such persons beneficially own.

To be timely, a stockholder must generally deliver notice:

•

in connection with an annual meeting of stockholders, not less than 120 nor more than 180 days prior to the date on which the annual meeting of stockholders was held in the immediately preceding year, but in the event that the date of the annual meeting is more than 30 days before or more than 60 days after the anniversary date of the preceding annual meeting of stockholders, a stockholder notice will be timely if received by us not later than the close of business on the later of (1) the 120th day prior to the annual meeting and (2) the 10th day following the day on which we first publicly announce the date of the annual meeting; or

•

in connection with the election of a director at a special meeting of stockholders, not less than 40 nor more than 60 days prior to the date of the special meeting, but in the event that less than 55 days’ notice or prior public disclosure of the date of the special meeting of the stockholders is given or made to the stockholders, a stockholder notice will be timely if received by us not later than the close of business on the 10th day following the day on which a notice of the date of the special meeting was mailed to the stockholders or the public disclosure of that date was made.

In order to submit a nomination for our Board of Directors, a stockholder must also submit any information with respect to the nominee that we would be required to include in a proxy statement, as well as certain other information. If a stockholder fails to follow the required procedures, the stockholder’s proposal or nominee will be ineligible and will not be voted on by our stockholders.

Limitation on Liability of Directors and Officers

Our restated certificate of incorporation provides that no director or officer will be personally liable to us or our stockholders for monetary damages for breach of fiduciary duties as a director or officer, except as required by applicable law, as in effect from time to time. Currently, Delaware law prohibits the elimination or limitation of liability of:

•

a director or officer for any breach of the director’s or officer’s duty of loyalty to our company or our stockholders;

•

a director or officer for any act or omission not in good faith or which involved intentional misconduct or a knowing violation of law;

•

a director for unlawful payments of dividends or unlawful stock repurchases or redemptions as provided in Section 174 of the Delaware General Corporation Law;

•

a director or officer for any transaction from which the director or officer derived an improper personal benefit; and

•

an officer in any action by or in the right of the company.

Our second amended and restated bylaws provide that, to the fullest extent permitted by law, we will indemnify any officer or director of our company against all damages, claims and liabilities arising out of the fact that the person is or was our director or officer, or served any other enterprise at our request as a director, officer, employee, agent or fiduciary. We will reimburse the expenses, including attorneys’ fees, incurred by a person indemnified by this provision when we receive an undertaking to repay such amounts if it is ultimately determined that the person is not entitled to be indemnified by us. Amending this provision will not reduce our indemnification obligations relating to actions taken before an amendment.

Limitation on Liability of Controlling Stockholders

Subject to certain exceptions, Delaware law provides that no person who is a controlling stockholder or member of a control group will be liable in such capacity to the company or its stockholders for monetary damages for breach of fiduciary duty other than for:

•

a breach of the duty of loyalty to the company or the other stockholders;

•

acts or omissions not in good faith or which involve intentional misconduct or a knowing violation of law; or

•

any transaction from which the person derived an improper personal benefit.

Anti-Takeover Effects of Some Provisions

Some provisions of our restated certificate of incorporation and second amended and restated bylaws could make the following more difficult:

•

acquisition of control of us by means of a proxy contest or otherwise; or

•

removal of our incumbent officers and directors.

These provisions, as well as our ability to issue preferred stock, are designed to discourage coercive takeover practices and inadequate takeover bids. These provisions are also designed to encourage persons seeking to acquire control of us to first negotiate with our Board of Directors. We believe that the benefits of increased protection give us the potential ability to negotiate with the proponent of an unfriendly or unsolicited proposal to acquire or restructure us, and that the benefits of this increased protection outweigh the disadvantages of discouraging those proposals, because negotiation of those proposals could result in an improvement of their terms.

Transactions and Corporate Opportunities

Our restated certificate of incorporation includes provisions that regulate and define the conduct of specified aspects of the business and affairs of our company. These provisions serve to determine and delineate the respective rights and duties of our company, our principal stockholder, TTWF LP, and any partner of TTWF LP, any person or entity that is controlled by TTWF LP, controls TTWF LP or is under common control with TTWF LP (other than Westlake and any of its subsidiaries) and any director, officer, employee or equity owner of any of such entities (such persons or entities, together with TTWF LP, the “principal stockholder affiliates”), and some of our directors and officers in anticipation of the following:

•

the principal stockholder affiliates serving as our directors and/or officers;

•

the principal stockholder affiliates engaging in lines of business that are the same as, or similar to, our lines of business;

•

the principal stockholder affiliates having an interest in the same areas of corporate opportunity as we have; and

•

we and the principal stockholder affiliates engaging in material business transactions.

We may enter into agreements with the principal stockholder affiliates to engage in any transaction. We may also enter into agreements with the principal stockholder affiliates to compete or not to compete with each other, including agreements to allocate, or to cause our directors, officers and employees and the principal stockholder affiliates to allocate, opportunities between the principal stockholder affiliates and us. Our restated certificate of incorporation provides that no such agreement will be considered contrary to any fiduciary duty of the principal stockholder affiliates, as our direct and indirect controlling stockholders, or our directors, officers or employees. Neither the principal stockholder affiliates nor any of our directors, officers or employees who are also principal stockholder affiliates are under any fiduciary duty to us to refrain from acting on our behalf or on behalf of the principal stockholder affiliates in respect of any such agreement or transaction. These provisions are generally subject to the corporate opportunity obligations described below with which the principal stockholder affiliates and our officers and directors who are also principal stockholder affiliates must comply.

Under our restated certificate of incorporation, the principal stockholder affiliates have no duty to refrain from engaging in activities or lines of business similar to ours or from doing business with any of our clients, customers or vendors and, except as discussed in the above paragraph, the principal stockholder affiliates will not be liable to us or our stockholders for breach of any fiduciary duty as a stockholder by reason of any of these activities. In addition, if the principal stockholder affiliates or one of our directors or officers who is also a principal stockholder affiliate acquires knowledge of a potential transaction or matter which may be a corporate opportunity for both our company and the principal stockholder affiliates, then neither the principal stockholder affiliates nor any such person will have a duty to communicate or offer this corporate opportunity to us and will not be liable to us or our stockholders for breach of any fiduciary duty by reason of the fact that the principal stockholder affiliates pursue or acquire the corporate opportunity for themselves, direct the corporate opportunity to another person or do not communicate information regarding the corporate opportunity to us, so long as the principal stockholder affiliates act in a manner consistent with the following policy: A corporate opportunity offered to the principal stockholder affiliates or to any person who is one of our officers or directors and who is also a principal stockholder affiliate will belong to the principal stockholder affiliates, unless the opportunity was expressly offered in writing to the principal stockholder affiliates solely in their capacity as direct and indirect stockholders of our company or to that person solely in his or her capacity as one of our directors or officers.

Anyone becoming one of our stockholders will be deemed to have notice of and consented to these provisions of our restated certificate of incorporation. Our restated certificate of incorporation provides that in no event shall any amendment of these provisions subject any principal stockholder affiliate to liability for any act or omission occurring prior to such amendment for which such person would be deemed not to be liable under these provisions prior to such amendment.

Delaware Business Combination Statute

We have expressly elected not to be subject to Section 203 of the General Corporation Law of the State of Delaware, which is described below. However, our stockholders can amend our restated certificate of incorporation and second amended and restated bylaws to elect to be subject to Section 203. Section 203 provides that, subject to specified exceptions, an interested stockholder of a Delaware corporation is not permitted to engage in any business combination, including mergers or consolidations or acquisitions of additional shares of the corporation, with the corporation for a three-year period following the time that stockholder became an interested stockholder, unless one of the following conditions is met:

•

prior to the time the stockholder became an interested stockholder, the Board of Directors approved either the business combination or the transaction that resulted in the stockholder becoming an interested stockholder;

•

upon consummation of the transaction that resulted in the stockholder becoming an interested stockholder, the interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction commenced, other than statutorily excluded shares; or

•

on or subsequent to the time the stockholder became an interested stockholder, the business combination is approved by the Board of Directors and authorized at an annual or special meeting of stockholders by the affirmative vote of at least 66 2/3% of the outstanding voting stock which is not owned by the interested stockholder.

Except as otherwise set forth in Section 203, “interested stockholder” means:

•

any person that is the owner of 15% or more of the outstanding voting stock of the corporation, or is an affiliate or associate of the corporation and was the owner of 15% or more of the outstanding voting stock of the corporation at any time within three years immediately prior to the date of determination; and

•

the affiliates and associates of any such person.

If we ever become subject to Section 203, it may be more difficult for a person who is an interested stockholder to effect various business combinations with us for the applicable three-year period. Section 203, if it becomes applicable, also may have the effect of preventing changes in our management. It is possible that Section 203, if it becomes applicable, could make it more difficult to accomplish transactions which our stockholders may otherwise deem to be in their best interests. The provisions of Section 203, if it becomes applicable, may cause persons interested in acquiring us to negotiate in advance with our Board of Directors. The restrictions on business combinations set forth in Section 203 are not applicable to the principal stockholder so long as the principal stockholder holds 15% or more of our outstanding shares of common stock. Because we are not currently subject to Section 203, the principal stockholder, as a controlling stockholder, may find it easier to sell its controlling interest to a third party because Section 203 would not apply to the third party.

Listing of Common Stock

Our common stock is listed on the New York Stock Exchange under the symbol “WLK.”

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Equiniti Trust Company, LLC.

DESCRIPTION OF WARRANTS

We may issue warrants to purchase debt securities, common stock, preferred stock or other securities or any combination of the foregoing. We may issue warrants independently or together with other securities. Warrants sold with other securities may be attached to or separate from the other securities. We will issue warrants under one or more warrant agreements between us and a warrant agent that we will name in the applicable prospectus supplement.

The prospectus supplement relating to any warrants that we may offer will include specific terms relating to the offering. We will file the form of any warrant agreement with the SEC, and you should read the warrant agreement for provisions that may be important to you. The applicable prospectus supplement will include some or all of the following terms:

•

the title of the warrants;

•

the aggregate number of warrants offered;

•

the designation, number and terms of the debt securities, common stock, preferred stock or other securities purchasable upon exercise of the warrants, and the procedures by which those numbers may be adjusted;

•

the exercise price of the warrants;

•

the dates or periods during which the warrants are exercisable;

•

the designation and terms of any securities with which the warrants are issued;

•

if the warrants are issued as a unit with another security, the date, if any, on and after which the warrants and the other security will be separately transferable;

•

if the exercise price is not payable in U.S. dollars, the foreign currency, currency unit or composite currency in which the exercise price is denominated;

•

any minimum or maximum amount of warrants that may be exercised at any one time; and

•

any terms, procedures and limitations relating to the transferability, exchange or exercise of the warrants.

SELLING STOCKHOLDER

In addition to covering the issuance and sale of securities by us, this prospectus covers the possible sale from time to time of up to 4,500,000 shares of our common stock by the selling stockholder listed below. As used in this prospectus, “selling stockholder” includes the successors-in-interest, donees, transferees or others who may later hold the selling stockholder’s interests and who will be named in the applicable supplement to this prospectus.

The following table sets forth information as of October 27, 2025 regarding the selling stockholder’s beneficial ownership of our common stock. Shares of stock are “beneficially owned” by a person if the person directly or indirectly has or shares the power to vote or dispose of the shares, regardless of whether the person has any economic interest in the shares. A person also beneficially owns shares as to which the person has the right to acquire beneficial ownership within 60 days.

Since the selling stockholder may sell none, all, or a portion of the 4,500,000 shares of our common stock included in the prospectus, no meaningful estimate can be given as to the amount or percentage of shares that will be held by the selling stockholder after completion of any sale by the selling stockholder.


Name and Address	Number of Shares Beneficially Owned		Percent of Stock (1)
TTWF LP (2)(3)		93,405,554		72.4	%

(1)	Calculated as of October 27, 2025 based on 128,273,152 shares of common stock outstanding.

(2)

The address of the selling stockholder is 2801 Post Oak Boulevard, Suite 600, Houston, Texas 77056. The selling stockholder may be deemed an “underwriter” within the meaning of the Securities Act of 1933, as amended (the “Securities Act”), with respect to sales of the shares of our common stock listed above.

(3)

TTWF LP, a Delaware limited partnership, holds 92,010,554 shares of our common stock and TTWFGP LLC, a Delaware limited liability company and the general partner of TTWF LP, holds 1,395,000 shares of our common stock. Two trusts for the benefit of members of the Chao family are the managers of TTWFGP LLC. Decisions regarding the voting and disposition of the securities held of record by TTWF LP and TTWFGP LLC are made by a committee comprised of members of the Chao family. No individual committee member can act alone to direct the voting or disposition of these securities. Each member of the committee disclaims beneficial ownership of the securities reported herein.

Registration Rights Agreement

We are party to a registration rights agreement with the selling stockholder under which we have agreed, at the request of the selling stockholder, to use our best efforts to register shares of our common stock that are held by the selling stockholder for public sale under the Securities Act. As long as the selling stockholder owns a majority of the voting power of our outstanding common stock, there is no limit to the number of registrations that it may request. Once the selling stockholder owns less than a majority of the voting power of our outstanding common stock, it can request a total of five additional registrations. We have also agreed in the registration rights agreement to provide the selling stockholder and its permitted transferees with “piggy-back” rights to include its shares in registrations of our common stock under the Securities Act. There is no limit on the number of these “piggy-back” registrations in which the selling stockholder may request its shares be included. These rights will terminate once the selling stockholder is able to dispose of all of its shares of our common stock within a three-month period pursuant to the exemption from registration provided under Rule 144 of the Securities Act. We have agreed to cooperate in these registrations and related offerings. We and the selling stockholder have agreed to restrictions on the ability of each party to sell securities following registrations by either party. The shares of our common stock that may be sold by the selling stockholder hereunder are included in this prospectus pursuant to the registration rights agreement.

PLAN OF DISTRIBUTION

We and the selling stockholder may sell the securities in and outside the United States (a) through underwriters or dealers, (b) directly to purchasers or (c) through agents. The applicable prospectus supplement will include the following information:

•

the terms of the offering;

•

the names of any underwriters or agents;

•

the purchase price of the securities from us or the selling stockholder and, if the purchase price is not payable in U.S. dollars, the currency, currency unit or composite currency in which the purchase price is payable;

•

the net proceeds to us or the selling stockholder from the sale of securities;

•

any delayed delivery arrangements;

•

any underwriting discounts, commissions and other items constituting underwriters’ compensation;

•

the initial public offering price;

•

any discounts or concessions allowed or reallowed or paid to dealers; and

•

any commissions paid to agents.

Sale Through Underwriters or Dealers

If we or the selling stockholder use underwriters in the sale of securities, the underwriters will acquire the securities for their own account. The underwriters may resell the securities from time to time in one or more transactions, including negotiated transactions, at a fixed public offering price or at varying prices determined at the time of sale. Underwriters may offer securities to the public either through underwriting syndicates represented by one or more managing underwriters or directly by one or more firms acting as underwriters. Unless we inform you otherwise in the applicable prospectus supplement, the obligations of the underwriters to purchase the securities will be subject to conditions, and the underwriters will be obligated to purchase all the offered securities if they purchase any of them. The underwriters may change from time to time any initial public offering price and any discounts or concessions allowed or reallowed or paid to dealers.

During and after an offering through underwriters, the underwriters may purchase and sell the securities in the open market. These transactions may include overallotment and stabilizing transactions and purchases to cover syndicate short positions created in connection with the offering. The underwriters also may impose a penalty bid, which means that selling concessions allowed to syndicate members or other broker-dealers for the offered securities sold for their account may be reclaimed by the syndicate if the offered securities are repurchased by the syndicate in stabilizing or covering transactions. These activities may stabilize, maintain or otherwise affect the market price of the offered securities, which may be higher than the price that might otherwise prevail in the open market. If commenced, the underwriters may discontinue these activities at any time.

If we or the selling stockholder use dealers in the sale of securities, the securities will be sold directly to them as principals. They may then resell those securities to the public at varying prices determined by the dealers at the time of resale. The dealers participating in any sale of the securities may be deemed to be underwriters within the meaning of the Securities Act with respect to any sale of those securities. We will include in the applicable prospectus supplement the names of the dealers and the terms of the transaction.

Direct Sales and Sales Through Agents

We or the selling stockholder may sell the securities directly. In that event, no underwriters or agents would be involved. We or the selling stockholder may also sell the securities through agents designated from time to

time. In the applicable prospectus supplement, we will name any agent involved in the offer or sale of the offered securities, and we will describe any commissions payable by us or the selling stockholder to the agent. Unless we inform you otherwise in the applicable prospectus supplement, any agent will agree to use its reasonable best efforts to solicit purchases for the period of its appointment.

We or the selling stockholder may sell the securities directly to institutional investors or others who may be deemed to be underwriters within the meaning of the Securities Act with respect to any sale of those securities. We or the selling stockholder will describe the terms of any such sales in the applicable prospectus supplement.

Private Sales

The shares of our common stock covered by this prospectus that may be sold by the selling stockholder qualify for sale pursuant to Rule 144 under the Securities Act and may be sold by the selling stockholder under Rule 144 rather than pursuant to this prospectus.

Delayed Delivery Contracts

If we so indicate in the applicable prospectus supplement, we or the selling stockholder may authorize agents, underwriters or dealers to solicit offers from certain types of institutions to purchase securities from us at the public offering price under delayed delivery contracts. These contracts would provide for payment and delivery on a specified date in the future. The contracts would be subject only to those conditions described in the applicable prospectus supplement. The applicable prospectus supplement will describe the commission payable for solicitation of those contracts.

Remarketing

We may offer and sell any of the securities in connection with a remarketing upon their purchase, in accordance with a redemption or repayment by their terms or otherwise, by one or more remarketing firms acting as principals for their own accounts or as our agents. We will identify any remarketing firm, the terms of any remarketing agreement and the compensation to be paid to the remarketing firm in the applicable prospectus supplement. Remarketing firms may be deemed underwriters under the Securities Act.

Derivative Transactions

We or the selling stockholder may enter into derivative transactions with third parties, or sell securities not covered by this prospectus to third parties in privately negotiated transactions. If the applicable prospectus supplement indicates, in connection with those derivatives, the third parties may sell securities covered by this prospectus and the applicable prospectus supplement, including in short sale transactions. If so, the third parties may use securities pledged by us or borrowed from us or others to settle those sales or to close out any related open borrowings of stock, and may use securities received from us in settlement of those derivatives to close out any related open borrowings of stock.

We, the selling stockholder or one of our respective affiliates may loan or pledge securities to a financial institution or other third party that in turn may sell the securities using this prospectus. Such financial institution or third party may transfer its short position to investors in our securities or in connection with a simultaneous offering of other securities offered by this prospectus or otherwise.

The third parties in any of the sale transactions described above will be underwriters and will be identified in the applicable prospectus supplement or in a post-effective amendment to the registration statement of which this prospectus forms a part.

General Information

We or the selling stockholder may have agreements with the agents, dealers and underwriters to indemnify them against certain civil liabilities, including liabilities under the Securities Act, or to contribute with respect to payments that the agents, dealers or underwriters may be required to make. Agents, dealers and underwriters may be customers of, engage in transactions with or perform services for us in the ordinary course of their businesses.

Pursuant to the registration rights agreement described under “Selling Stockholder,” we have agreed to pay all of the costs, fees and expenses incurred by us incident to our registration of the resale of the selling stockholder’s common stock, as well as legal fees and expenses of counsel to the selling stockholder. We will not pay any commissions, fees and discounts of underwriters, brokers, dealers and agents with respect to shares of our common stock sold by the selling stockholder.

LEGAL MATTERS

In connection with particular offerings of the securities in the future, certain legal matters will be passed upon for us by Baker Botts L.L.P., Houston, Texas. Any underwriters will be advised about other issues relating to any offering by their own legal counsel, which firm will be named in the applicable prospectus supplement.

EXPERTS

The financial statements and management’s assessment of the effectiveness of internal control over financial reporting (which is included in Management’s Report on Internal Control over Financial Reporting) incorporated in this Prospectus by reference to the Annual Report on Form 10-K for the year ended December 31, 2024 have been so incorporated in reliance on the report of PricewaterhouseCoopers LLP, an independent registered public accounting firm, given on the authority of said firm as experts in auditing and accounting.

WHERE YOU CAN FIND MORE INFORMATION

Our website is located at http://www.westlake.com. Our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other filings with the SEC are available, free of charge, through our website, as soon as reasonably practicable after those reports or filings are electronically filed with or furnished to the SEC. Information on or accessible through our website or any other website is not incorporated by reference in this prospectus and does not constitute a part of this prospectus.

This prospectus is part of a registration statement we have filed with the SEC relating to the securities we and the selling stockholder may sell. As permitted by SEC rules, this prospectus does not contain all of the information we have included in the registration statement and the accompanying exhibits and schedules we file with the SEC. You may refer to the registration statement, the exhibits and the schedules for more information about us, the selling stockholder and our securities. The registration statement, exhibits and schedules are available through the SEC’s website.

We incorporate by reference the documents listed below and any future filings we make with the SEC under Section 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), until we sell all the securities offered by this prospectus, excluding any information “furnished” but not “filed,” unless we specifically provide that such “furnished” information is to be incorporated by reference:

•

our annual report on Form 10-K for the fiscal year ended December 31, 2024, including the portions of our definitive proxy statement on Schedule 14A filed with the SEC on March 28, 2025 that are incorporated by reference therein;

•

our quarterly reports on Form 10-Q for the quarters ended March 31, 2025, June 30, 2025, and September 30, 2025;

•

our current reports on Form 8-K filed with the SEC on March 4, 2025, April 16, 2025, May 12, 2025 and June 17, 2025; and

•

the description of our common stock contained in our Registration Statement on Form 8-A filed with the SEC on July 30, 2004, as updated by the description of our common stock included in Exhibit 4.1 to our Annual Report on Form 10-K for the fiscal year ended December 31, 2023, and as we may further update that description from time to time.

We will provide a copy of any and all of the information that is incorporated by reference in this prospectus to any person, including a beneficial owner, to whom this prospectus is delivered, without charge, upon written or oral request. You may obtain a copy of these filings (other than an exhibit to those filings unless we have specifically incorporated that exhibit by reference into the filing), at no cost, by writing or telephoning us at the following address:

Westlake Corporation

2801 Post Oak Boulevard, Suite 600

Houston, Texas 77056

Attention: Investor Relations

Telephone: (713) 960-9111

LOGO

Westlake Corporation

$ % Senior Notes due 20

Preliminary Prospectus Supplement

Joint Book-Running Managers

BofA Securities

Deutsche Bank Securities

J.P. Morgan

Wells Fargo Securities

November , 2025

Source: View Original Filing on SEC EDGAR

FAQ

What is Westlake (WLK) offering in this 424B5?

Westlake is offering two series of senior unsecured notes, with final aggregate principal amounts, coupons and maturities to be determined at pricing.

How will Westlake use the note proceeds?

Westlake plans to fund the repurchase of its 3.600% Senior Notes due 2026, with $750 million outstanding as of September 30, 2025, and use any remaining proceeds for the €82.5 million ACI acquisition and general corporate purposes.

When does the tender offer for the 2026 notes expire?

The tender offer is expected to expire on November 10, 2025, unless extended or earlier terminated.

Will the new notes be listed on an exchange?

No. Westlake does not intend to apply for listing of either series on any securities exchange or automated dealer quotation system.

What is the ranking of the new senior notes?

They are senior unsecured obligations ranking equally with Westlake’s other senior unsecured indebtedness and effectively subordinated to secured debt and subsidiary liabilities.

Are there redemption or change of control provisions?

Yes. Westlake may redeem the notes as described, and upon a Change of Control Triggering Event, it must offer to repurchase the notes at 101% of principal plus accrued interest.

What are the issuance denominations and form?

The notes will be issued in registered, book-entry form in minimum denominations of $2,000 and integral multiples of $1,000.

Trending News

[424B5] WESTLAKE CORP Prospectus Supplement (Debt Securities)

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