<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2012-12-11</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001479094</issuerCik>
        <issuerName>STAG Industrial, Inc.</issuerName>
        <issuerTradingSymbol>STAG</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001517392</rptOwnerCik>
            <rptOwnerName>Sullivan Gregory W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O STAG INDUSTRIAL, INC.</rptOwnerStreet1>
            <rptOwnerStreet2>99 HIGH STREET, 28TH FLOOR</rptOwnerStreet2>
            <rptOwnerCity>BOSTON</rptOwnerCity>
            <rptOwnerState>MA</rptOwnerState>
            <rptOwnerZipCode>02110</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>CFO, EVP and Treasurer</officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock</value>
            </securityTitle>
            <transactionDate>
                <value>2012-12-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>28155</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>127704</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Partnership Units</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <footnoteId id="F2"/>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2012-12-11</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>C</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
                <footnoteId id="F1"/>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>28155</value>
                </transactionShares>
                <transactionPricePerShare>
                    <footnoteId id="F4"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2012-04-20</value>
                <footnoteId id="F3"/>
            </exerciseDate>
            <expirationDate>
                <footnoteId id="F3"/>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.01 per share</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>28155</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">The reporting person redeemed 28,155 common units of limited partnership interests (&quot;OP Units&quot;) in STAG Industrial Operating Partnership, L.P., a Delaware limited partnership (&quot;Operating Partnership&quot;), of which STAG Industrial, Inc., a Maryland corporation (&quot;Issuer&quot;), is the sole member of the general partner. The OP Units are redeemable for cash equal to the then current market value of one share of the Issuer's common stock or, at the election of the Issuer, for shares of the Issuer's common stock on a one-for-one basis.  The Issuer elected to redeem the reporting person's OP Units with common stock.  The OP Units have no expiration date.</footnote>
        <footnote id="F2">This represents OP Units in the Operating Partnership.  The OP Units are redeemable for cash equal to the then current market value of one share of the Issuer's common stock or, at the election of the Issuer, for shares of the Issuer's common stock on a one-for-one basis.  The OP Units have no expiration date.</footnote>
        <footnote id="F3">The OP Units are vested as of the date of issuance and have no expiration date.</footnote>
        <footnote id="F4">The OP Units are redeemable for cash equal to the then current market value of one share of the Issuer's common stock or, at the election of the Issuer, for shares of the Issuer's common stock on a one-for-one basis.  The OP Units have no expiration date.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Kathryn Arnone, Attonrey-in-Fact</signatureName>
        <signatureDate>2012-12-11</signatureDate>
    </ownerSignature>
</ownershipDocument>
