Page 1

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K ( Mark One ) X ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 25 , 2020 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 000-50646 Ultra Clean Holdings , Inc. ( Exact name of Registrant as specified in its charter ) Delaware ( State or other jurisdiction of incorporation or organization ) 26462 Corporate Avenue Hayward , California ( Address of principal executive offices ) Registrant's telephone number , including area code : ( 510 ) 576-4400 Securities registered pursuant to Section 12 ( b ) of the Act : Title of Each Class Common Stock , $ 0.001 par value 冈 Securities registered pursuant to Section 12 ( g ) of the Act : None 61-1430858 ( IRS Employer Identification No. ) Name of Each Exchange on Which Registered The NASDAQ Global Market LLC 94545 ( Zip Code ) No O No 区 Indicate by check mark if the registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . Yes > 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 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 O 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 .: Large accelerated filer Non - accelerated filer DOCUMENTS INCORPORATED BY REFERENCE 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 by Rule 12b - 2 of the Act ) . Yes No | The aggregate market value of the voting and non - voting stock held by non - affiliates of the Registrant , based on the closing sale price of the Registrant's common stock on June 26 , 2020 as reported on the NASDAQ Global Market , was approximately $ 865.9 million . Shares of common stock held by each executive officer and director have been excluded from this computation . The determination of affiliate status for this purpose is not necessarily a conclusive determination for other purposes . Number of shares of the registrant's common stock outstanding as of February 19 , 2021 : 40,612,933 Portions of the registrant's definitive proxy statement to be delivered to stockholders in connection with the 2020 annual meeting of stockholders are incorporated by reference in Part III of this Form 10 - K where indicated . Such proxy statement will be filed with the Securities and Exchange Commission within 120 days of the registrant's fiscal year ended December 25 , 2020 .