<SUBMISSION>
<ACCESSION-NUMBER>0001179110-18-004399
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20180313
<FILING-DATE>20180315
<DATE-OF-FILING-DATE-CHANGE>20180315
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>JONES TERRELL B
<CIK>0001219057
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>001-35155
<FILM-NUMBER>18693643
</FILING-VALUES>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>BOINGO WIRELESS INC
<CIK>0001169988
<ASSIGNED-SIC>4899
<IRS-NUMBER>000000000
<STATE-OF-INCORPORATION>DE
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>10960 WILSHIRE BLVD., 23RD FLOOR
<CITY>LOS ANGELES
<STATE>CA
<ZIP>90024
<PHONE>310-586-5180
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>10960 WILSHIRE BLVD., 23RD FLOOR
<CITY>LOS ANGELES
<STATE>CA
<ZIP>90024
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>edgar.xml
<DESCRIPTION>FORM 4 -
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0306</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2018-03-13</periodOfReport>

    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0001169988</issuerCik>
        <issuerName>BOINGO WIRELESS INC</issuerName>
        <issuerTradingSymbol>WIFI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001219057</rptOwnerCik>
            <rptOwnerName>JONES TERRELL B</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>C/O BOINGO WIRELESS INC.</rptOwnerStreet1>
            <rptOwnerStreet2>10960 WILSHIRE BLVD 23RD FL</rptOwnerStreet2>
            <rptOwnerCity>LOS ANGELES</rptOwnerCity>
            <rptOwnerState>CA</rptOwnerState>
            <rptOwnerZipCode>90024</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>2018-03-13</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>S</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>12500</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>27.19</value>
                    <footnoteId id="F1"/>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>D</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>65183</value>
                    <footnoteId id="F2"/>
                    <footnoteId id="F3"/>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </nonDerivativeTransaction>
    </nonDerivativeTable>

    <derivativeTable></derivativeTable>

    <footnotes>
        <footnote id="F1">This transaction was executed in multiple sales through a sales order executed by a broker-dealer at prices ranging from $27.06 to $27.33. The price reported in this column reflects the weighted average sale price. The Reporting Person will provide upon request to the SEC staff, the Issuer, or a security holder of the Issuer, full information regarding the number of shares sold at each separate price.</footnote>
        <footnote id="F2">Reflects shares owned by the Terrell B Jones Rev Trust, which the Reporting Person is trustee and beneficiary.</footnote>
        <footnote id="F3">The amount of shares beneficially owned by the Reporting Person was incorrectly reported on prior Reports. This number reflects an increase of 7,669 shares and represents the correct number of shares beneficially owned.</footnote>
    </footnotes>

    <ownerSignature>
        <signatureName>/s/ Efren Medina as Attorney-in-Fact for Terrell Jones</signatureName>
        <signatureDate>2018-03-15</signatureDate>
    </ownerSignature>
</ownershipDocument>
</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
