Rayon d'Or (1876–1896) was a French Thoroughbred racehorse and Champion sire in the United States.
Bred by Frédéric Lagrange at his Haras de Dangu stud farm in Dangu, Eure, he was sired by Flageolet whose wins included the Prix Morny (1872), Goodwood Cup (1873) and Jockey Club Cup (1873) and whom Rayon d'Or would help make the Leading sire in Great Britain and Ireland in 1879.
Rayon d'Or raced from age two through four, winning important races in England and France at distances of one mile to mile and a quarter such as the Sussex and Champion Stakes, and at endurance distances such as the 4,000 meter Prix du Cadran at Longchamp Racecourse and the Prix Rainbow at 5,000 meters.
He was purchased by American businessman, and former member of the United States House of Representatives, William Scott.
Rayon d'Or was brought to the United States to stand at Scott's Algeria Stock Farm at Erie, Pennsylvania, where he sired most of his major winners.