Joseph Cyril O'Brien (June 25, 1917 - September 29, 1984) was a Harness racing driver, trainer and owner who won the U.S. Trotting Triple Crown in 1955 and would be inducted into both the U.S. Harness Racing Hall of Fame and the Canadian Horse Racing Hall of Fame, as well as Canada's Sports Hall of Fame. Noted for his quiet dignity and diplomacy, he is considered one of the greatest harness horsemen in history.