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UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K × ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR □ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Commission file number 1-31763 KRONOS WORLDWIDE , INC . ( Exact name of Registrant as specified in its charter ) DELAWARE ( State or other jurisdiction of incorporation or organization ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common stock to 5430 LBJ Freeway , Suite 1700 Dallas , Texas 75240-2620 ( Address of principal executive offices ) Registrant's telephone number , including area code : ( 972 ) 233-1700 Trading Symbol ( s ) 76-0294959 ( IRS Employer Identification No. ) Indicate by check mark : If the Registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes KRO No securities are registered pursuant to Section 12 ( g ) of the Act . Name of each exchange on which registered NYSE No > If the Registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes No > Whether the Registrant ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes No ☐☐☐ Whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T during the preceding 12 months ( or for such shorter period that the Registrant was required to submit such files ) . Yes No Whether the Registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , smaller reporting company or an emerging growth company . See the definitions of " large accelerated filer , " " accelerated filer , " " smaller reporting company , " and " emerging growth company ” in Rule 12b 2 of the Exchange Act . Large accelerated filer Non - accelerated filer Accelerated filer > Smaller reporting company ☐ Emerging growth company If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . □ Whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Whether the Registrant is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes No > The aggregate market value of the 22.2 million shares of voting stock held by nonaffiliates of Kronos Worldwide , Inc. as of June 30 , 2020 ( the last business day of the Registrant's most recently - completed second fiscal quarter ) approximated $ 231.1 million . Number of shares of the registrant's common stock , $ .01 par value per share , outstanding on February 26 , 2021 : 115,542,717 . Documents incorporated by reference The information required by Part III is incorporated by reference from the Registrant's definitive proxy statement to be filed with the Commission pursuant to Regulation 14A not later than 120 days after the end of the fiscal year covered by this report .