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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 September 30 , 2021 or TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the transition period from to Commission File Number 1-5667 Cabot Corporation ( Exact name of Registrant as specified in its Charter ) Delaware ( State or other jurisdiction of incorporation or organization ) Two Seaport Lane , Suite 1400 Boston , Massachusetts ( Address of Principal Executive Offices ) 04-2271897 ( I.R.S. Employer Identification No. ) 02210 ( Zip Code ) Registrant's telephone number , including area code : ( 617 ) 345-0100 Securities registered pursuant to Section 12 ( b ) of the Securities Exchange Act of 1934 : Title of each class Trading symbol ( s ) Name of each exchange on which registered The New York Stock Exchange Common Stock , $ 1 par value per share CBT Securities registered pursuant to Section 12 ( g ) of the Securities Exchange Act of 1934 : None . Indicate by check mark if the Registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes X 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 X 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 . No Yes x 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 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 checkmark 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 . 000 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 > As of the last business day of the Registrant's most recently completed second fiscal quarter ( March 31 , 2021 ) , the aggregate market value of the Registrant's common stock held by non - affiliates was $ 2,956,431,066 . As of November 15 , 2021 , there were 56,803,284 shares of the Registrant's common stock outstanding . Portions of the Registrant's definitive proxy statement for its 2022 Annual Meeting of Shareholders are incorporated by reference into Part III of this report .