Euchre ( /ˈjuːkər/) or eucre, is a trick-taking card game most commonly played with four people in two partnerships with a deck of 24 standard playing cards. It is the game responsible for introducing the joker into modern packs; this was invented around 1860 to act as a top trump or best bower (from the German word Bauer, "farmer", denoting also the jack). It is believed to be closely related to the French game Écarté that was popularized in the United States by the Cornish and Pennsylvania Dutch, and to the seventeenth-century game of bad repute Loo. It may be sometimes referred to as Knock Euchre to distinguish it from Bid Euchre.

Euchre appears to have been introduced into the United States by the early German settlers of the state of Michigan, and from that state gradually to have been disseminated throughout the nation. It has been more recently theorized that the game and its name derives from an eighteenth-century Alsatian card game named Juckerspiel, a derivative of Triomphe. Also, it may have been introduced by immigrants from Cornwall, England, where it still remains a popular game. It is also played in the neighboring county of Devon, where one theory is that it was introduced by French or American prisoners of war imprisoned in Dartmoor prison during the early 19th century. Ombre is an ancestral form of Euchre.