Blackjack (formerly black jack and vingt-un) is a casino banking game. It is the most widely played casino banking game in the world. It uses decks of 52 cards and descends from a global family of casino banking games known as "twenty-one".

Thought to derive from another popular card game called Chemin de Fer, also originating in French casinos, Blackjack was first known as Vingt-et-Un, which simply translates to Twenty-One.