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

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2015-03-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001568319</issuerCik>
        <issuerName>Voltari Corp</issuerName>
        <issuerTradingSymbol>VLTC</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0000921669</rptOwnerCik>
            <rptOwnerName>ICAHN CARL C</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O ICAHN ASSOCIATES HOLDING LLC</rptOwnerStreet1>
            <rptOwnerStreet2>767 FIFTH AVE., SUITE 4700</rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10153</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>1</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001 (&quot;Shares&quot;)</value>
            </securityTitle>
            <transactionDate>
                <value>2015-03-30</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>X</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>4061417</value>
                    <footnoteId id="F4"/>
                </transactionShares>
                <transactionPricePerShare>
                    <value>1.36</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>4739620</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>please see footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Subscription Rights (&quot;right to buy&quot;)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>1.36</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2015-03-30</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>X</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>678203</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0.00</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <value>2015-02-27</value>
            </exerciseDate>
            <expirationDate>
                <value>2015-03-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Shares</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>4061417</value>
                    <footnoteId id="F4"/>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>0</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>I</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value>please see footnotes</value>
                    <footnoteId id="F1"/>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">High River Limited Partnership (&quot;High River&quot;) is the direct beneficial owner of: (i) 698,848 Shares; (ii) 142,966 Shares underlying warrants; and (iii) 168,995 shares of Series J preferred stock of Voltari Corporation (formerly Motricity, Inc.) (the &quot;Issuer&quot;). Koala Holding LP (&quot;Koala&quot;) is the direct beneficial owner of: (i) 4,040,772 Shares; (ii) 826,637 Shares underlying warrants; and (iii) 977,136 shares of Series J preferred stock of the Issuer.</footnote>
        <footnote id="F2">Hopper Investments, LLC (&quot;Hopper&quot;) is the general partner of High River. Koala Holding GP Corp. (&quot;Koala GP&quot;) is the general partner of Koala. Barberry Corp. (&quot;Barberry&quot;) is the sole member of Hopper and the sole stockholder of Koala GP. Carl C. Icahn is the sole stockholder of Barberry. As such, Mr. Icahn is in a position indirectly to determine the investment and voting decisions made by each of the foregoing entities.</footnote>
        <footnote id="F3">Each of Hopper, Barberry and Mr. Icahn (by virtue of their relationship to High River) may be deemed to indirectly beneficially own the Shares which High River owns. Each of Hopper, Barberry and Mr. Icahn disclaims beneficial ownership of such Shares except to the extent of their pecuniary interest therein. Each of Koala GP, Barberry and Mr. Icahn (by virtue of their relationship to Koala) may be deemed to indirectly beneficially own the Shares which Koala owns. Each of Koala GP, Barberry and Mr. Icahn disclaims beneficial ownership of such Shares except to the extent of their pecuniary interest therein.</footnote>
        <footnote id="F4">Represents Shares acquired upon exercise of basic subscription rights and oversubscription rights allocated to High River and Koala in the rights offering conducted by the Issuer, which expired on March 20, 2015. The acquisition of the subscription rights by High River and Koala was exempt from Section 16 by virtue of Rule 16a-9(b) and the purchase of Shares by High River and Koala pursuant to the exercise of the subscription rights was exempt from Section 16(b) by virtue of Section 16b-6(b).</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>CARL C. ICAHN</signatureName>
        <signatureDate>2015-03-31</signatureDate>
    </ownerSignature>
</ownershipDocument>
