UNITED STATES SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 10-K x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 HEIDRICK & STRUGGLES INTERNATIONAL, INC. (Exact Name of Registrant as Specified in its Charter) (State or Other Jurisdiction of Incorporation or Organization) For the fiscal year ended December 31, 2018 Delaware 36-2681268 OR (I.R.S. Employer Identification Number) ¨ TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) SECURITIES EXCHANGE ACT O ...