<SEC-DOCUMENT>0001020569-19-000085.txt : 20190221
<SEC-HEADER>0001020569-19-000085.hdr.sgml : 20190221
<ACCEPTANCE-DATETIME>20190221190230
ACCESSION NUMBER:		0001020569-19-000085
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20190219
FILED AS OF DATE:		20190221
DATE AS OF CHANGE:		20190221

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			Meaney William L
		CENTRAL INDEX KEY:			0001566391

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	001-13045
		FILM NUMBER:		19623571

	MAIL ADDRESS:	
		STREET 1:		C/O IRON MOUNTAIN INCORPORATED
		STREET 2:		ONE FEDERAL STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			IRON MOUNTAIN INC
		CENTRAL INDEX KEY:			0001020569
		STANDARD INDUSTRIAL CLASSIFICATION:	REAL ESTATE INVESTMENT TRUSTS [6798]
		IRS NUMBER:				232588479
		STATE OF INCORPORATION:			DE
		FISCAL YEAR END:			1231

	BUSINESS ADDRESS:	
		STREET 1:		ONE FEDERAL STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110
		BUSINESS PHONE:		617-535-4781

	MAIL ADDRESS:	
		STREET 1:		ONE FEDERAL STREET
		CITY:			BOSTON
		STATE:			MA
		ZIP:			02110

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	IRON MOUNTAIN INC/PA
		DATE OF NAME CHANGE:	20000201

	FORMER COMPANY:	
		FORMER CONFORMED NAME:	PIERCE LEAHY CORP
		DATE OF NAME CHANGE:	19960807
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>wf-form4_155079373650805.xml
<DESCRIPTION>FORM 4
<TEXT>
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    <periodOfReport>2019-02-19</periodOfReport>

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    <issuer>
        <issuerCik>0001020569</issuerCik>
        <issuerName>IRON MOUNTAIN INC</issuerName>
        <issuerTradingSymbol>IRM</issuerTradingSymbol>
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    <reportingOwner>
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            <rptOwnerName>Meaney William L</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O IRON MOUNTAIN INCORPORATED</rptOwnerStreet1>
            <rptOwnerStreet2>ONE FEDERAL STREET</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02110</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
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        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>President and CEO</officerTitle>
            <otherText></otherText>
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            <transactionDate>
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            </transactionDate>
            <transactionCoding>
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                <transactionCode>M</transactionCode>
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        <nonDerivativeTransaction>
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        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.01 per share</value>
            </securityTitle>
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                <value>2019-02-19</value>
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                <transactionCode>M</transactionCode>
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                    <footnoteId id="F3"/>
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                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
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                <sharesOwnedFollowingTransaction>
                    <value>206108</value>
                </sharesOwnedFollowingTransaction>
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                </directOrIndirectOwnership>
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        </nonDerivativeTransaction>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $.01 per share</value>
            </securityTitle>
            <transactionDate>
                <value>2019-02-19</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>F</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>22783</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>35.39</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
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                <sharesOwnedFollowingTransaction>
                    <value>183325</value>
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                <value>Common Stock, par value $.01 per share</value>
            </securityTitle>
            <transactionDate>
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            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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            <transactionAmounts>
                <transactionShares>
                    <value>8621</value>
                    <footnoteId id="F4"/>
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                    <value>35.28</value>
                    <footnoteId id="F5"/>
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    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Restricted Stock Units</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F6"/>
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            <transactionDate>
                <value>2019-02-19</value>
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                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                    <value>25105</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
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                <footnoteId id="F7"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F7"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
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                <transactionCode>M</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
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                    <value>18225</value>
                </transactionShares>
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                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>18225.0</value>
                </underlyingSecurityShares>
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                <sharesOwnedFollowingTransaction>
                    <value>18280</value>
                </sharesOwnedFollowingTransaction>
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                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
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        </derivativeTransaction>
        <derivativeTransaction>
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            <conversionOrExercisePrice>
                <footnoteId id="F9"/>
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                <transactionFormType>4</transactionFormType>
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                <transactionShares>
                    <value>52113</value>
                </transactionShares>
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                    <value>0</value>
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                    <value>D</value>
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                <footnoteId id="F10"/>
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                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>52113.0</value>
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                    <value>0</value>
                </sharesOwnedFollowingTransaction>
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    <footnotes>
        <footnote id="F1">This acquisition is reported to reflect the partial vesting of restricted stock units (&quot;RSUs&quot;) previously granted to the Reporting Person on February 18, 2016.</footnote>
        <footnote id="F2">This acquisition is reported to reflect the partial vesting of RSUs previously granted to the Reporting Person on February 16, 2017.</footnote>
        <footnote id="F3">This acquisition is reported to reflect the full vesting of performance units (&quot;PUs&quot;) previously granted to the Reporting Person on February 18, 2016. Effective February 14, 2019, the Compensation Committee of Iron Mountain Incorporated's Board of Directors (the &quot;Compensation Committee&quot;) determined the actual award of PUs under the grant after completion of the relevant performance period, and the PUs vested in full on February 18, 2019.</footnote>
        <footnote id="F4">This transaction was effected pursuant to a 10b5-1 trading plan which was approved and became effective as of May 3, 2018.</footnote>
        <footnote id="F5">The price reported in Column 4 is a weighted average price. These shares of Iron Mountain Incorporated common stock (&quot;Common Stock&quot;) were sold in multiple transactions at prices ranging from $35.17 to $35.39, inclusive. The Reporting Person undertakes to provide Iron Mountain Incorporated (the &quot;Company&quot;), any security holder of the Company, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares of Common Stock sold at each separate price within the ranges set forth in this footnote (5).</footnote>
        <footnote id="F6">Each RSU represents a contingent right to receive one share of Common Stock.</footnote>
        <footnote id="F7">The RSUs, representing a contingent right to receive a total of 75,162 shares of Common Stock, were granted to the Reporting Person on February 18, 2016 and have vested in full.</footnote>
        <footnote id="F8">The RSUs, representing a contingent right to receive a total of 54,729 shares of Common Stock, were granted to the Reporting Person on February 16, 2017 and vest in three substantially equal annual installments beginning on the first anniversary of the grant date.</footnote>
        <footnote id="F9">Each PU represents a contingent right to receive one share of Common Stock.</footnote>
        <footnote id="F10">The PUs were initially granted to the Reporting Person on February 18, 2016. Effective February 14, 2019, the Compensation Committee determined the actual award of PUs under the grant after completion of the relevant performance period, and the PUs vested in full on February 18, 2019.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>/s/ Elizabeth Tammaro, under Power of Attorney dated May 26, 2016, from William Meaney</signatureName>
        <signatureDate>2019-02-21</signatureDate>
    </ownerSignature>
</ownershipDocument>
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</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
