Derby (därˈbē) [key], English horse race, instituted (1780) by the 12th earl of Derby and held annually at Epsom Downs, near London. The race is open only to three-year-old colts and fillies that must be entered when yearlings. The original course is still used; it is one yard longer than one and one-half miles. Hundreds of thousands of spectators view the race each year. Other well-known races, notably the Kentucky Derbydûrˈbē, held each year since 1875 at Churchill Downs, Louisville, Ky., have been named for the English classic.