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( Mark One ) X UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OK ( State or other jurisdiction of Incorporation or Organization ) FORM 10 - K TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from Bank of Oklahoma Tower Boston Avenue at Second Street ОК Tulsa , ( Address of Principal Executive Offices ) to OR Commission File No. 0-19341 BOK FINANCIAL CORP ( Exact name of registrant as specified in its charter ) 73-1373454 ( IRS Employer Identification No. ) 74172 ( Zip Code ) ( 918 ) 588-6000 ( Registrant's telephone number , including area code ) Securities registered pursuant to Section 12 ( b ) of the Act : None Securities registered pursuant to Section 12 ( g ) of the Act : Common stock , $ 0.00006 par value Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes ý No □ Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15 ( d ) of the Act . Yes No ý 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 y No Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Website , if any , every Interactive Data File required to be submitted and posted 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 and post such files ) Yes ý No Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S - K is not contained herein , and will not be contained , to the best of registrant's knowledge , in definitive proxy or information statements incorporated by reference in Part III of this Form 10 - K or any amendment to this Form 10 - K . Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer or a smaller reporting company . See definitions of " larger accelerated filer , " " accelerated filer " and " smaller reporting company " in Rule 12b - 2 of the Exchange Act . ( Check one ) : Large Accelerated Filer ý Accelerated filer ¨ Non - 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 is a shell company ( as defined in Rule 12b - 2 of the Act ) . Yes No ý 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 . DOCUMENTS INCORPORATED BY REFERENCE The aggregate market value of the registrant's common stock ( " Common Stock " ) held by non - affiliates is approximately $ 1.8 billion ( based on the June 30 , 2020 closing price of Common Stock of $ 56.44 per share ) . As of January 31 , 2021 , there were 69,577,615 shares of Common Stock outstanding . Part III incorporates certain information by reference from the Registrant's Proxy Statement for the 2021 Annual Meeting of Shareholders .