A derby is a type of competition, often a race or rivalry match, that carries special excitement and meaning.

The most famous derbies are horse races. The Kentucky Derby, held every May in Louisville, is one of the most celebrated sporting events in America. Thoroughbred horses that have trained for years compete in a thrilling race while thousands of spectators watch, many wearing elaborate hats and fancy clothes. Other countries have their own famous derbies, like England's Epsom Derby.

In sports, a derby often means a match between two teams from the same city or region. When the Yankees play the Mets, New Yorkers call it the Subway Series, a kind of derby. In English soccer, matches between Liverpool and Everton are called the Merseyside Derby because both teams come from the same area. These games feel more intense than regular matches because of the local pride at stake.

The word also refers to a men's hat with a rounded crown and narrow brim, though most people today call this style a bowler hat. In the early 1900s, well-dressed gentlemen commonly wore derbies.