Some famous racehorses include Triple Crown winners Secretariat, War Admiral and Affirmed. Two of the most famous racehorses of the 21st century are former Triple Crown contenders Barbaro and Smarty Jones.
Man O' War is another famous racehorse of the 20th century. He is known for only having lost a single race in his career, and he probably only lost that one because he became turned around in the starting gate and thus started the race facing backwards. Despite that difficult start, he finished in second place. He also sired many other excellent racehorses, including War Admiral.
Seabiscuit is another famous racehorse. He is known for being an underdog, in part because of his odd conformation and gait. His early career was marked by poor performances, but the right trainer and jockey turned him around and he became a popular hero in the 1930s. He won a special matched race against War Admiral in 1939.
Citation is not such a popularly known horse, but he is famous for winning the Triple Crown and becoming the first racehorse to win more than one million dollars in his career. Sir Barton is also famous among racing fans for becoming the first horse ever to win the Triple Crown in 1919.
Ruffian was one of the most famous fillies in racing history. She won her first 10 races and was expected to have a brilliant career. However, like Barbaro, she suffered a catastrophic injury in her 3-year-old year and had to be euthanized.