Exo ( /ˌɛks ˈəʊ/ EKS-oh; Korean: 엑소; stylized as EXO) is a Chinese-South Korean boy band produced by S.M. Entertainment. Formed in 2011 in Seoul, South Korea, Exo comprises twelve members separated into two subgroups, Exo-K and Exo-M, promoting their music simultaneously in both South Korea and China respectively. Their name was taken from exoplanet, a term referring to planets outside of the Solar System. Their debut single "Mama" was released on April 8, 2012, followed by the release of their debut EP Mama on April 9, 2012.

In January 2011, producer Lee Soo-man of S.M. Entertainment announced his plans to debut a new boy band in March or April 2011. Temporarily named M1, the group appeared to have consisted of only seven members when a photo of them in a dance studio leaked online. In May 2011, Lee spoke about the group in a Hallyu business seminar held in Stanford University. In the presentation, he explained his strategy of separating the group into two subgroups, M1 and M2, and have them promote the same music in both Korea and China, performing the songs in both Korean and Mandarin. Lee planned to launch the group in May 2011, but their debut was delayed and news concerning the group did not surface until October 2011, when Lee briefly discussed about the group's concept plans in an interview with The Chosun Ilbo.