American Flag (1922–1942) was an American Thoroughbred racehorse. Bred and raced by Samuel D. Riddle, who owned his sire, Man o' War, he was out of the dam Lady Comfey. Trained by Gwyn Tompkins, as a two-year-old American Flag's most important performance was a win in the Manor Stakes at Laurel Park Racecourse in Laurel, Maryland. Undefeated at age three, he had important wins in the Withers and Dwyer Stakes plus he captured what became known as the third leg of the U.S. Triple Crown series, the Belmont Stakes. His 1925 performances earned him Champion Three-Year-Old colt honors.