<SEC-DOCUMENT>0000902664-25-004829.txt : 20251110
<SEC-HEADER>0000902664-25-004829.hdr.sgml : 20251110
<ACCEPTANCE-DATETIME>20251110180515
ACCESSION NUMBER:		0000902664-25-004829
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20251106
FILED AS OF DATE:		20251110
DATE AS OF CHANGE:		20251110

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			JANA Partners Management, LP
		CENTRAL INDEX KEY:			0001998597
		ORGANIZATION NAME:           	
		STATE OF INCORPORATION:			DE

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-41194
		FILM NUMBER:		251467684

	BUSINESS ADDRESS:	
		STREET 1:		888 SEVENTH AVENUE
		STREET 2:		24TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10106
		BUSINESS PHONE:		212-455-0900

	MAIL ADDRESS:	
		STREET 1:		888 SEVENTH AVENUE
		STREET 2:		24TH FLOOR
		CITY:			NEW YORK
		STATE:			NY
		ZIP:			10106

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			MERCURY SYSTEMS INC
		CENTRAL INDEX KEY:			0001049521
		STANDARD INDUSTRIAL CLASSIFICATION:	ELECTRONIC COMPONENTS & ACCESSORIES [3670]
		ORGANIZATION NAME:           	04 Manufacturing
		EIN:				042741391
		STATE OF INCORPORATION:			MA
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		50 MINUTEMAN ROAD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810
		BUSINESS PHONE:		9782561300

	MAIL ADDRESS:	
		STREET 1:		50 MINUTEMAN ROAD
		CITY:			ANDOVER
		STATE:			MA
		ZIP:			01810

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	MERCURY COMPUTER SYSTEMS INC
		DATE OF NAME CHANGE:	19971112
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>ownership.xml
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0508</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2025-11-06</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001049521</issuerCik>
        <issuerName>MERCURY SYSTEMS INC</issuerName>
        <issuerTradingSymbol>MRCY</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001998597</rptOwnerCik>
            <rptOwnerName>JANA Partners Management, LP</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>888 SEVENTH AVENUE</rptOwnerStreet1>
            <rptOwnerStreet2>24TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10106</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>1</isOther>
            <officerTitle></officerTitle>
            <otherText>See Remarks</otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <aff10b5One>0</aff10b5One>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2025-11-06</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionTimeliness></transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>1000000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>75.45</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4966675</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>See footnote</value>
                    <footnoteId id="F2"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The transaction reported herein was effected for the purpose of rebalancing the holdings of funds and accounts managed by JANA (as defined below).</footnote>
        <footnote id="F2">JANA Partners Management, LP (&quot;JANA&quot; or the &quot;Reporting Person&quot;) 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 &quot;GP&quot;) 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.</footnote>
    </footnotes>

    <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 Scott Ostfeld, a Managing Partner and Portfolio Manager of the Reporting Person, currently serves on the board of directors of the Issuer.</remarks>

    <ownerSignature>
        <signatureName>/s/ JANA Partners Management, LP, by Jennifer Fanjiang, Partner, Chief Legal Officer and Chief Compliance Officer</signatureName>
        <signatureDate>2025-11-10</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
