A piano quartet is a musical ensemble consisting of a piano and three other instruments, or a piece written for such a group. In classical music, those other instruments are usually a string trio, that is a violin, viola and cello.

Piano quartets for that standard lineup were written by Wolfgang Amadeus Mozart, Robert Schumann, Johannes Brahms, Antonín Dvořák and Gabriel Fauré among others. In the 20th century, composers have written for more varied groups, with Anton Webern's Quartet, opus 22 (1930), for example, being for piano, violin, clarinet and tenor saxophone, and Olivier Messiaen's Quatuor pour la fin du temps (1940) for piano, violin, cello and clarinet.