Gainsborough (1915–1945) was a British bred Thoroughbred racehorse who won the English Triple Crown in 1918 and became a superior sire.

The Triple Crown of Thoroughbred Racing, often shortened to Triple Crown, is a series of horse races for Thoroughbreds, often restricted to three-year-olds. Winning all three of these Thoroughbred horse races is considered the greatest accomplishment in Thoroughbred racing. The term originated in mid-19th-century England and nations where Thoroughbred racing is popular each have their own Triple Crown series.