A girl group is a popular music act featuring several young female singers who generally harmonise together.

Girl groups emerged in the late 1950s as groups of young singers teamed up with behind-the-scenes songwriters and music producers to create hit singles, often featuring glossy production values and backing by top studio musicians. Some acts had certain members taking the lead vocalist position with the other members as supporting vocalists. In later eras the girl group template would be applied to disco, contemporary R&B, and country-based formats as well as pop.

A distinction is made here with all-female bands, in which members also play instruments, though this terminology is not universally followed.

Spice Girls and TLC are considered the best-selling girl groups of all time. Both of their sales records have surpassed any other girl group in the world and their albums (Spice Girls' Spice and TLC's CrazySexyCool) are the best-selling albums of all time by a girl group.