<SUBMISSION>
<ACCESSION-NUMBER>0001181431-03-012116
<TYPE>4
<PUBLIC-DOCUMENT-COUNT>1
<PERIOD>20030626
<FILING-DATE>20030701
<REPORTING-OWNER>
<OWNER-DATA>
<CONFORMED-NAME>SIEGEL RICHARD W
<CIK>0001195154
</OWNER-DATA>
<FILING-VALUES>
<FORM-TYPE>4
<ACT>34
<FILE-NUMBER>000-22333
<FILM-NUMBER>03765969
</FILING-VALUES>
<MAIL-ADDRESS>
<STREET1>1319 MARQUETTE DR
<CITY>ROMEOVILLE
<STATE>IL
<ZIP>60441
</MAIL-ADDRESS>
</REPORTING-OWNER>
<ISSUER>
<COMPANY-DATA>
<CONFORMED-NAME>NANOPHASE TECHNOLOGIES CORPORATION
<CIK>0000883107
<ASSIGNED-SIC>3390
<IRS-NUMBER>363687863
<STATE-OF-INCORPORATION>IL
<FISCAL-YEAR-END>1231
</COMPANY-DATA>
<BUSINESS-ADDRESS>
<STREET1>453 COMMERCE ST
<CITY>BURR RIDGE
<STATE>IL
<ZIP>60521
<PHONE>6303231200
</BUSINESS-ADDRESS>
<MAIL-ADDRESS>
<STREET1>453 COMMERCE STREET
<CITY>BURR RIDGE
<STATE>IL
<ZIP>60521
</MAIL-ADDRESS>
</ISSUER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>rrd12017.xml
<DESCRIPTION>FORM 4
<TEXT>
<XML>
<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0101</schemaVersion>

    <documentType>4</documentType>
<periodOfReport>2003-06-26</periodOfReport>
<notSubjectToSection16>0</notSubjectToSection16>
    <issuer>
        <issuerCik>0000883107</issuerCik>
        <issuerName>NANOPHASE TECHNOLOGIES CORPORATION</issuerName>
        <issuerTradingSymbol>NANX</issuerTradingSymbol></issuer>
<reportingOwner>
<reportingOwnerId>
            <rptOwnerCik>0001195154</rptOwnerCik>
            <rptOwnerName>SIEGEL RICHARD W</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>  </rptOwnerStreet1>
            <rptOwnerStreet2>  </rptOwnerStreet2>
            <rptOwnerCity>  </rptOwnerCity>
            <rptOwnerState>  </rptOwnerState>
            <rptOwnerZipCode>  </rptOwnerZipCode>
        </reportingOwnerAddress>
            <reportingOwnerRelationship>
<isDirector>1</isDirector>
<isOfficer>0</isOfficer>
<isTenPercentOwner>0</isTenPercentOwner>
<isOther>0</isOther>
<officerTitle></officerTitle>
<otherText></otherText></reportingOwnerRelationship></reportingOwner>
<nonDerivativeSecurity>
<securityTitle>
<value>Common Stock</value></securityTitle>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionTimeliness>
<value></value></transactionTimeliness>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>200527</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></nonDerivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>0.112</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1995-02-15</value>
<footnoteId id="F1"/></exerciseDate>
<expirationDate>
<value>2004-02-15</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>14475</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>14475</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>0.432</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1996-02-01</value>
<footnoteId id="F1"/></exerciseDate>
<expirationDate>
<value>2005-02-01</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>17370</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>17370</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>1.727</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1997-03-01</value>
<footnoteId id="F1"/></exerciseDate>
<expirationDate>
<value>2006-03-01</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>13896</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>13896</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>3.886</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1997-11-07</value>
<footnoteId id="F2"/></exerciseDate>
<expirationDate>
<value>2006-11-07</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>23160</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>23160</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>5.250</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1999-06-10</value>
<footnoteId id="F3"/></exerciseDate>
<expirationDate>
<value>2008-06-10</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>2000</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>2000</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>3.8125</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>1999-07-31</value>
<footnoteId id="F1"/></exerciseDate>
<expirationDate>
<value>2008-07-31</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>11600</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>11600</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>9.920</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>2002-06-05</value>
<footnoteId id="F3"/></exerciseDate>
<expirationDate>
<value>2011-06-05</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>2000</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>2000</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>3.780</value></conversionOrExercisePrice>
<transactionDate>
<value>1988-08-08</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>0</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>2003-11-25</value>
<footnoteId id="F3"/></exerciseDate>
<expirationDate>
<value>2012-11-25</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>2000</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>2000</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<derivativeSecurity>
<securityTitle>
<value>Common Stock (right to buy)</value></securityTitle>
<conversionOrExercisePrice>
<value>5.07</value></conversionOrExercisePrice>
<transactionDate>
<value>2003-06-26</value></transactionDate>
<transactionCoding>
<transactionFormType>4</transactionFormType>
<transactionCode>A</transactionCode>
<equitySwapInvolved>0</equitySwapInvolved></transactionCoding>
<transactionAmounts>
<transactionShares>
<value>2000</value></transactionShares>
<transactionValue>
<value>0</value></transactionValue>
<transactionAcquiredDisposedCode>
<value>A</value></transactionAcquiredDisposedCode></transactionAmounts>
<exerciseDate>
<value>2004-06-26</value>
<footnoteId id="F3"/></exerciseDate>
<expirationDate>
<value>2013-06-26</value></expirationDate>
<underlyingSecurity>
<underlyingSecurityTitle>
<value>Common Stock</value></underlyingSecurityTitle>
<underlyingSecurityShares>
<value>2000</value></underlyingSecurityShares></underlyingSecurity>
<postTransactionAmounts>
<sharesOwnedFollowingTransaction>
<value>2000</value></sharesOwnedFollowingTransaction></postTransactionAmounts>
<ownershipNature>
<directOrIndirectOwnership>
<value>D</value></directOrIndirectOwnership>
<natureOfOwnership>
<value></value></natureOfOwnership></ownershipNature></derivativeSecurity>
<footnotes>
<footnote id="F1">Subject to certain restrictions, beginning on this date, the options vest in five equal annual installments.</footnote>
<footnote id="F2">Subject to certain restrictions, 19,177 of these options vest in five equal annual installments beginning on 11/7/97, with the remainder vesting on 11/7/04.</footnote>
<footnote id="F3">Subject to certain restrictions, beginning on this date, the options vest in three equal annual installments.</footnote></footnotes>
<ownerSignature>
<signatureName>By Jess Jankowski, under UPA, for Richard W. Siegel</signatureName>
<signatureDate>2003-06-30</signatureDate></ownerSignature></ownershipDocument>


</XML>
</TEXT>
</DOCUMENT>
</SUBMISSION>
