Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response... 0.5

(Print or Type Responses)

1. Name and Address of Reporting Person * JANA Partners Management, LP 2. Issuer Name and Ticker or Trading Symbol MERCURY SYSTEMS INC [MRCY] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) __X__ Other (specify below) See Remarks (Last) (First) (Middle) 888 SEVENTH AVENUE, 24TH FLOOR 3. Date of Earliest Transaction (Month/Day/Year) 10/22/2025 (Street) NEW YORK, NY 10106 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock, par value $0.01 per share 10/22/2025 A 2,362(1) A $ 0 5,966,675 I See footnotes(2)(3)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
	Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB control number.		SEC 1474 (9-02)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
JANA Partners Management, LP 888 SEVENTH AVENUE 24TH FLOOR NEW YORK, NY 10106	X			See Remarks

Signatures

/s/ JANA Partners Management, LP, by Jennifer Fanjiang, Partner, Chief Legal Officer and Chief Compliance Officer		10/24/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Represents deferred stock units ("DSUs") that vest on the earlier of the first anniversary of the grant date and the next annual meeting of shareholders. Vested DSUs do not convert into shares of common stock until the date on which Scott Ostfeld ("Mr. Ostfeld"), the Managing Partner of JANA Partners Management, LP ("JANA" or the "Reporting Person") ceases to be a member of the Issuer's board of directors.
(2)	Mr. Ostfeld has assigned all rights to any shares issuable pursuant to the grant to the Reporting Person. Pursuant to the assignment, settlement of the award on vesting will be made to the Reporting Person.
(3)	JANA is a private money management firm which beneficially owns the securities reported herein through various accounts under its management and control. JANA Partners Management GP, LLC (the "GP") is the general partner of JANA. Barry Rosenstein is the Founder of the GP and JANA. JANA, the GP and Barry Rosenstein disclaim any beneficial ownership of any of the Issuer's securities reported herein except to the extent of their pecuniary interest therein, if any.
Remarks: The Reporting Person may be deemed to be a director by deputization for purposes of Section 16 under the Securities Exchange Act of 1934 by virtue of the fact that Mr. Ostfeld, a Managing Partner and Portfolio Manager of of the Reporting Person, currently serves on the board of directors of the Issuer.

Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure. Potential persons who are to respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB number.