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

    <schemaVersion>X0303</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2008-09-30</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000891103</issuerCik>
        <issuerName>IAC/INTERACTIVECORP</issuerName>
        <issuerTradingSymbol>IACI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001243087</rptOwnerCik>
            <rptOwnerName>RATTNER STEVEN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>375 PARK AVE. 14TH FL.</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>NEW YORK</rptOwnerCity>
            <rptOwnerState>NY</rptOwnerState>
            <rptOwnerZipCode>10152</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle></officerTitle>
            <otherText></otherText>
        </reportingOwnerRelationship>
    </reportingOwner>

    <nonDerivativeTable>
        <nonDerivativeTransaction>
            <securityTitle>
                <value>Common Stock, par value $0.001</value>
            </securityTitle>
            <transactionDate>
                <value>2008-09-30</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>785</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>17.30</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>20351</value>
                    <footnoteId id="F1"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable>
        <derivativeHolding>
            <securityTitle>
                <value>Restricted Stock Units</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2007-06-20</value>
            </exerciseDate>
            <expirationDate>
                <value>2009-06-20</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Commom Stock, par value $0.001</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>2865</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>2865</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Restricted Stock Units</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2008-06-13</value>
            </exerciseDate>
            <expirationDate>
                <value>2010-06-13</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.001</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>5730</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>5730</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
        <derivativeHolding>
            <securityTitle>
                <value>Restricted Stock Units</value>
                <footnoteId id="F2"/>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>0</value>
            </conversionOrExercisePrice>
            <exerciseDate>
                <value>2009-08-01</value>
            </exerciseDate>
            <expirationDate>
                <value>2011-08-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock, par value $0.001</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>8594</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>8594</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeHolding>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">Includes (i) 785 share units accrued under the Non-Employee Director Deferred Compensation Plan as of September 30, 2008, plus (ii) 9,564 share units previously accrued under the Non-Employee Director Deferred Compensation Plan prior to September 30, 2008, which number reflects adjustments made to such units (in the same manner as those made to restricted stock units (see footnote 2 below)) to reflect the one-for-two reverse stock split (the &quot;Reverse Stock Split&quot;) effected in connection with, and immediately following, the spin-off by IAC of HSN, Inc., Interval Leisure Group, Inc., Ticketmaster and Tree.com, Inc. on August 20, 2008 (the &quot;Spin-Off&quot;), plus (iii) 10,002 shares of IAC common stock held by the reporting person, which number reflects adjustments to give effect to the Reverse Stock Split effected in connection with, and immediately following, the Spin-Off.</footnote>
        <footnote id="F2">Reflects previously granted restricted stock units with adjustments (to maintain pre- and post-Spin-Off values) to the number of shares of IAC common stock underlying such restricted stock units, to reflect the Spin-Off and Reverse Stock Split. These previously granted restricted stock units have the same vesting and other applicable terms and conditions as they did immediately prior to the Spin-off and Reverse Stock Split.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>Joanne Hawkins as Attorney-in-Fact for Steven Rattner</signatureName>
        <signatureDate>2008-10-02</signatureDate>
    </ownerSignature>
</ownershipDocument>

