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X ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K For the transition period from Delaware ( State or other jurisdiction of incorporation or organization ) 27422 Portola Parkway , Suite 200 Foothill Ranch , California ( Address of principal executive offices ) Title of each class Common stock , par value $ 0.01 per share KAISER ALUMINUM CORPORATION ( Exact name of registrant as specified in its charter ) Large accelerated filer Non - accelerated filer to Commission File Number : 1-09447 ( 949 ) 614-1740 ( Registrant's telephone number , including area code ) Securities Registered Pursuant to Section 12 ( b ) of the Act : Trading symbol 冈 94-3030279 ( I.R.S. Employer Identification No. ) 92610-2831 ( Zip Code ) KALU Securities Registered Pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes No Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of Act . Yes No Indicate by check mark 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 ( or for such shorter period that the registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . Yes > No Name of each exchange on which registered Nasdaq Global Select Market Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the registrant was required to submit such files ) . Yes No Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , a 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 : 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 . Indicate by check mark 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 . < Indicate by check mark whether the registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . Yes No The aggregate market value of the registrant's common stock held by non - affiliates of the registrant as of the last business day of the registrant's most recently completed second fiscal quarter ( June 30 , 2020 ) was approximately $ 1.1 billion . As of February 22 , 2021 , there were 15,812,169 shares of the Common Stock of the registrant outstanding . Documents Incorporated by Reference . Certain portions of the registrant's definitive proxy statement related to the registrant's 2021 annual meeting of stockholders are incorporated by reference into Part III of this Annual Report on Form 10 - K .