UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-Q Table of Contents x QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the quarterly period ended March 31, 2019 OR o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 1-16725 (Commission file number) PRINCIPAL FINANCIAL GROUP, INC. (Exact name of registrant as specified in its charter) (State or other jurisdiction of incorporation or organization) ...