Wonder Girls (Korean: 원더걸스) was a South Korean girl group formed by JYP Entertainment. The group debuted in February 2007 with the single "Irony" and 5 members: Yeeun, Sunye, Sunmi, Hyuna and Sohee. After Hyuna's departure in July, Yubin was added into the group prior to the release of their debut studio album, The Wonder Years (2007). The album spawned the hit single "Tell Me", which topped various South Korean music charts.

A girl group is a music act featuring several female singers who generally harmonize together. The term "girl group" is also used in a narrower sense in the United States to denote the wave of American female pop music singing groups, many of whom were influenced by doo-wop and which flourished in the late 1950s and early 1960s between the decline of early rock and roll and start of the British Invasion. All-female bands, in which members also play instruments, are usually considered a separate phenomenon. These groups are sometimes called "girl bands" to differentiate, although this terminology is not universally followed.