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

    <schemaVersion>X0202</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2007-11-09</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001024109</issuerCik>
        <issuerName>WESTSIDE ENERGY CORP</issuerName>
        <issuerTradingSymbol>WHT</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001202234</rptOwnerCik>
            <rptOwnerName>WILLIAMSON HERBERT C III</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/C COMMANCHERO - 4 RANCH</rptOwnerStreet1>
            <rptOwnerStreet2>P.O. BOX 260</rptOwnerStreet2>
            <rptOwnerCity>HUNT</rptOwnerCity>
            <rptOwnerState>TX</rptOwnerState>
            <rptOwnerZipCode>78024</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</value>
            </securityTitle>
            <transactionDate>
                <value>2007-11-09</value>
            </transactionDate>
            <deemedExecutionDate></deemedExecutionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>100000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>117966</value>
                    <footnoteId id="F2"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <footnotes>
        <footnote id="F1">The Reporting Person has acquired or will be acquiring within 60 days after the date of this filing these shares of the common stock of Westside Energy Corporation (the &quot;Company&quot;), pursuant to the Company's 2007 Equity Incentive Plan, for services provided to the Company as a director, valued at a per-share price of $2.65, the closing price of the Company's common stock on the dte of grant.</footnote>
        <footnote id="F2">Of these shares, 17,966 were issued pursuant to the Company's 2005 Director Stock Plan. Of these shares, 15,317 are currently vested, 1,766 may become vested on March 30, 2008 and 883 amy become vested on March 30, 2009. Of these shares, 100,000 were issued pursuant to the Company's 2007 Equity Incentive Plan. Of these 100,000 shares, one-third of these shares may become vested on January 1, 2008, one-third may become vested on January 1, 2009, and one-third may become vested on January 1, 2011.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Herbert C. Williamson III</signatureName>
        <signatureDate>2007-11-14</signatureDate>
    </ownerSignature>
</ownershipDocument>
