Mill Reef (1968–1986) was a Champion Thoroughbred racehorse and sire. He was bred in the United States but was trained in the United Kingdom throughout his racing career which lasted from 1970 to 1972. Mill Reef won twelve of his fourteen races and finished second in the other two. He was an outstanding two-year-old in 1970, and proved even better at three, winning the Epsom Derby, the Eclipse Stakes, the King George VI and Queen Elizabeth Stakes and the Prix de l'Arc de Triomphe. He won both his starts as a four-year-old before his racing career was ended by injury.