<Page> SECURITIES AND EXCHANGE COMMISSION WASHINGTON, D.C. 20549 FORM 8-K CURRENT REPORT Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934 Date of Report (Date of earliest event reported): May 27, 2003 Citigroup Inc. (Exact name of registrant as specified in its charter) DELAWARE 1-9924 52-1568099 (State or other (Commission (IRS Employer jurisdiction of File Number) Identification incorporation) Number) 399 PARK AVENUE, NEW YORK, NEW YORK 10043 (Address of principal executive offices) (Zip Code) (212) 559-1000 (Registrant's telephone number, including area code) <Page> CITIGROUP INC. Current Report on Form 8-K Item 5. OTHER EVENTS. Attached hereto as Exhibit 99.01 and incorporated by reference herein is the Historical Supplement of Citigroup Inc. and subsidiaries. Item 7. FINANCIAL STATEMENTS, PRO FORMA FINANCIAL INFORMATION AND EXHIBITS. (a) Not applicable. (b) Not applicable. (c) Exhibits <Table> <Caption> Exhibit Number Description of Exhibit - -------------- ---------------------- 99.01 Historical Supplement </Table> <Page> SIGNATURE Pursuant to the requirements of the Securities Exchange Act of 1934, the Registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized. CITIGROUP INC. Dated: May 27, 2003 By: /s/ William P. Hannon --------------------- William P. Hannon Controller and Chief Accounting Officer