Masimo Corp. Schedule 13G: Pentwater Capital Management reports beneficial ownership of 3,176,000 shares of Common Stock, representing 6.1% of the class. The percentage is calculated on 52,362,808 shares outstanding as of March 31, 2026, as reported in a Form 8-K cited in the filing.
The shares are held by the Pentwater Funds with shared voting and dispositive power reported; Matthew Halbower is disclosed as the sole shareholder of the investment manager's general partner and joined the joint filing.
Positive
None.
Negative
None.
Insights
Pentwater reports a meaningful passive stake in Masimo at 6.1%
Pentwater Capital Management LP discloses beneficial ownership of 3,176,000 shares held by the Pentwater Funds, with shared voting and dispositive power. The filing is a passive ownership disclosure under Schedule 13G rather than an active solicitation filing.
Ownership is measured against an outstanding share base of March 31, 2026. Future filings may show changes if Pentwater adjusts its position; this filing itself does not describe planned transactions or changes in intent.
Key Figures
Shares beneficially owned:3,176,000 sharesPercent of class:6.1%Shares outstanding used:52,362,808 shares+1 more
4 metrics
Shares beneficially owned3,176,000 sharesHeld by the Pentwater Funds (reported on Schedule 13G)
Percent of class6.1%Calculated on 52,362,808 shares outstanding as of March 31, 2026
Shares outstanding used52,362,808 sharesOutstanding shares as of <date>March 31, 2026</date> (per cited Form 8-K)
CUSIP574795100Masimo Corp. Common Stock CUSIP in filing
"The information required by Item 4(a) is set forth in Row 9 of the cover page"
Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.
Shared dispositive powerregulatory
"Shared Dispositive Power 3,176,000.00"
Investment Managerfinancial
"Pentwater Capital Management LP (the "Investment Manager"), a Delaware limited partnership"
Schedule 13Gregulatory
"Item 1. (a) Name of issuer: Masimo Corp."
A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
Masimo Corp.
(Name of Issuer)
Common Stock, par value $0.001 per share
(Title of Class of Securities)
574795100
(CUSIP Number)
03/31/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
574795100
1
Names of Reporting Persons
Pentwater Capital Management LP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
DELAWARE
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
3,176,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,176,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,176,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
6.1 %
12
Type of Reporting Person (See Instructions)
IA, PN
SCHEDULE 13G
CUSIP Number(s):
574795100
1
Names of Reporting Persons
Matthew Halbower
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
3,176,000.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
3,176,000.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
3,176,000.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
6.1 %
12
Type of Reporting Person (See Instructions)
HC, IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Masimo Corp.
(b)
Address of issuer's principal executive offices:
52 Discovery, Irvine, California, 92618
Item 2.
(a)
Name of person filing:
This statement is filed by:
(i) Pentwater Capital Management LP (the "Investment Manager"), a Delaware limited partnership, and the investment adviser to certain funds (the "Pentwater Funds"), with respect to the shares of common stock, par value $0.001 per share ("Common Stock") of Masimo Corp., a Delaware corporation (the "Company") directly held by the Pentwater Funds; and
(ii) Mr. Matthew Halbower ("Mr. Halbower"), the sole shareholder of MCH PWCM Holdings Inc., the general partner of the Investment Manager, with respect to the shares of Common Stock directly held by the Pentwater Funds.
The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons."
The filing of this statement should not be construed as an admission that any of the foregoing persons or any Reporting Person is, for the purposes of Section 13 of the Securities and Exchange Act of 1934, the beneficial owner of the securities reported herein.
(b)
Address or principal business office or, if none, residence:
The address of the business office of each of the Reporting Persons is 1001 10th Avenue South, Suite 216, Naples, FL 34102.
(c)
Citizenship:
The Investment Manager is a Delaware limited partnership. Mr. Halbower is a citizen of the United States.
(d)
Title of class of securities:
Common Stock, par value $0.001 per share
(e)
CUSIP Number(s):
574795100
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 52,362,808 shares of Common Stock outstanding as of March 31, 2026, as reported in the Company's Current Report on Form 8-K, filed with the Securities and Exchange Commission on May 4, 2026.
(b)
Percent of class:
6.1%
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
(ii) Shared power to vote or to direct the vote:
The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
(iii) Sole power to dispose or to direct the disposition of:
The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
(iv) Shared power to dispose or to direct the disposition of:
The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required.
See Item 2(a). The Pentwater Funds have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the shares of Common Stock reported herein.
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
Not Applicable
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
Pentwater Capital Management LP
Signature:
/s/ Matthew Halbower
Name/Title:
By: MCH PWCM Holdings Inc., General Partner, By: Matthew Halbower, Chief Executive Officer
Pentwater reports beneficial ownership of 3,176,000 shares of MASI, equal to 6.1% of the class. This percentage uses 52,362,808 shares outstanding as of March 31, 2026 per the filing.
Who filed the Schedule 13G for MASI?
The Schedule 13G was filed jointly by Pentwater Capital Management LP (the Investment Manager) and Matthew Halbower, the sole shareholder of the general partner, as stated in the filing.
Does the filing state Pentwater has sole voting control of MASI shares?
No. The filing reports shared voting power and shared dispositive power for 3,176,000 shares; it lists zero sole voting or sole dispositive power for the reporting persons.
What share count was used to calculate the 6.1% for MASI?
The percentage is calculated using 52,362,808 shares outstanding as of March 31, 2026, a figure cited from the Company’s Form 8-K referenced in the Schedule 13G.
