Stuart Errol Ungar was an American professional poker, blackjack, and gin rummy player, widely regarded to have been the greatest gin player of all time and one of the best Texas hold 'em players.

Gin rummy, or simply gin, is a two-player card game variant of rummy. It has enjoyed widespread popularity as both a social and a gambling game, especially during the mid twentieth century, and remains today one of the most widely-played two-player card games.