Jass (German pronunciation: [ˈjas]) is a family of trick taking, Ace-Ten card games and, in its key forms, a distinctive branch of the Marriage family. It is popular in its native Switzerland as well as the rest of the Alemannic German-speaking area of Europe, Italian South Tyrol and in a few places in Wisconsin and Ohio, USA.

The most common variant of Jass is Schieber (in Vorarlberg also known as Krüzjass), which is played by two teams of two players each. It is often considered Switzerland's national card game, and is so popular there that the Swiss have come to apply the name Jass to trick-taking card games in general.

It is estimated that there are over 70 variants of Jass. The game is so widespread in Switzerland that it is regularly featured on radio and television, for example, radio programmes by SRF1 and the weekly television programmes of Donnschtig Jass ("Thursday Jass") and Samschtig Jass ("Saturday Jass") on Schweizer Fernsehen. An estimated 3 million Swiss play Jass regularly and it has been described as a Swiss national game.