[8-K] MPLX LP Reports Material Event

Rhea-AI Filing Summary

MPLX LP filed an 8-K reporting that it has added several exhibits to its Form S-3 registration statement. The filing includes an underwriting agreement naming J.P. Morgan Securities LLC, Goldman Sachs & Co. LLC, BofA Securities, Inc., Mizuho Securities USA LLC, TD Securities (USA) LLC and Wells Fargo Securities, LLC as representatives of the underwriters; four supplemental indentures (Thirty-Second through Thirty-Fifth) with The Bank of New York Mellon Trust Company, N.A. as trustee that include forms of note; and a legal opinion and consent from Jones Day. These exhibits establish the legal and underwriting framework to issue multiple series of notes, but the filing does not disclose offering sizes, interest rates, maturities or other financial terms.

Positive

• Filed an Underwriting Agreement naming major underwriting firms (J.P. Morgan, Goldman Sachs, BofA, Mizuho, TD Securities, Wells Fargo), indicating an organized syndicate.
• Filed four supplemental indentures (Thirty-Second through Thirty-Fifth) that include forms of note with The Bank of New York Mellon Trust Company, N.A. as trustee, establishing the legal structure to issue multiple note series.

Negative

• The filing does not disclose offering sizes, interest rates, maturities or other economic terms, preventing assessment of financial impact.
• No financial statements, proceeds estimates, or use-of-proceeds information are included in the 8-K.

Insights

Securities Capital Markets Analyst

TL;DR: MPLX has filed underwriting and indenture documents needed to issue note series; material financial terms are not disclosed.

The filing formally attaches an underwriting agreement with a multi-bank syndicate and four supplemental indentures that include forms of note, plus counsel opinion and consent. Those documents are standard steps to enable public note issuances under a Form S-3 registration. Because the filing omits offering size, coupon, maturity and related economic terms, the market impact cannot be gauged from this report alone.

Corporate Securities Counsel

TL;DR: Legal and structural items are in place—underwriter agreement, trustee indentures and counsel opinion—while material terms remain absent from the filing.

The exhibits identified—an underwriting agreement, Thirty-Second through Thirty-Fifth Supplemental Indentures with The Bank of New York Mellon Trust Company, N.A. as trustee, and an opinion and consent from Jones Day—reflect completion of documentation required for issuance of multiple note series. The presence of a trustee and a firm legal opinion is consistent with market-standard governance and enforceability practices. Key economic details necessary for investor assessment are not included in this 8-K.

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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): August 11, 2025

MPLX LP

(Exact name of registrant as specified in its charter)

Delaware		001-35714		27-0005456
(State or other jurisdiction of incorporation)		(Commission File Number)		(IRS Employer Identification No.)

200 E. Hardin Street, Findlay, Ohio 45840

(Address of principal executive offices) (Zip code)

Registrant’s telephone number, including area code:(419) 422-2121

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading symbol(s)		Name of each exchange on which registered
Common Units Representing Limited Partnership Interests		MPLX		New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events.

MPLX LP (the “Issuer”) is filing herewith the following exhibits to its Registration Statement on Form S-3 (Registration No. 333-271922):

1. Underwriting Agreement, dated as of August 7, 2025, by and among the Issuer, MPLX GP LLC, the general partner of the Issuer, and each of J.P. Morgan Securities LLC, Goldman Sachs & Co. LLC, BofA Securities, Inc., Mizuho Securities USA LLC, TD Securities (USA) LLC and Wells Fargo Securities, LLC, acting as representatives of the several underwriters named therein;

2. Thirty-Second Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note);

3. Thirty-Third Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note);

4. Thirty-Fourth Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note);

5. Thirty-Fifth Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note); and

6. Opinion of Jones Day.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit Number		Description
1.1		Underwriting Agreement, dated as of August 7, 2025, by and among the Issuer, MPLX GP LLC, the general partner of the Issuer, and each of J.P. Morgan Securities LLC, Goldman Sachs & Co. LLC, BofA Securities, Inc., Mizuho Securities USA LLC, TD Securities (USA) LLC and Wells Fargo Securities, LLC, acting as representatives of the several underwriters named therein
4.1		Thirty-Second Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note)
4.2		Thirty-Third Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note)
4.3		Thirty-Fourth Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note)
4.4		Thirty-Fifth Supplemental Indenture, dated as of August 11, 2025, by and between the Issuer and The Bank of New York Mellon Trust Company, N.A., as Trustee (including Form of Note)
5.1		Opinion of Jones Day
23.1		Consent of Jones Day (included in Exhibit 5.1)
104		Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

				MPLX LP
				By:		MPLX GP LLC, its General Partner
Date: August 11, 2025				By:		/s/ Molly R. Benson
						Name: Molly R. Benson
						Title: Chief Legal Officer and Corporate Secretary