A derby is a type of horse race, named after the Epsom Derby, still run at Epsom racecourse, England, which was in turn named for Edward Smith Stanley, 12th Earl Of Derby, who inaugurated the race in 1780. Probably the best-known example in the United States is the Kentucky Derby. See also horse and Triple Crown of Thoroughbred Racing.

By extension from horse racing, derby is also used for any type of individual competitive event, such as a roller derby. In Britain, it is used (often in the form local derby) to mean a football match between local rival teams. For example, the North London derby is Arsenal versus Spurs.