Theme music is a piece that is often written specifically for a radio program, television program, video game or movie, and usually played during the title sequence and/or end credits. If it is accompanied by lyrics, most often associated with the show, it is a theme song.

The phrase theme song or signature tune may also be used to refer to a song that has become especially associated with a particular performer or dignitary; often used as they make an entrance.

The purpose of a theme song is often similar to that of a leitmotif.