U2 (IPA: /ˌjuːˈtuː/) are a rock band from Dublin, Ireland. The band consists of Bono (vocals and guitar), The Edge (guitar, keyboards and vocals), Adam Clayton (bass guitar), and Larry Mullen Jr. (drums and percussion). U2 have been one of the most popular acts in the world since the mid-1980s. The band has sold more than 170 million albums worldwide, and has won 22 Grammy Awards, more than any other rock band.

U2 formed in 1976 when the members were teenagers with limited musical proficiency. By the mid-1980s, however, the band had become a top international act, noted for its anthemic sound, Bono's impassioned vocals, The Edge's textural guitar playing, and a toned and in-time rhythm section. Their success as a live act was greater than their success as a record-selling act until their 1987 album, The Joshua Tree, brought them mega-stardom. Their 1991 album Achtung Baby and the accompanying Zoo TV Tour were part of a significant reinvention for the band; it was a response to their own sense of musical stagnation, the dance and alternative rock revolutions, and criticism of their image. This experimentation continued for the rest of the 1990s.

In the early years of the 21st century, U2 have pursued a more traditional sound while maintaining influences from their previous musical explorations. They continue to enjoy high levels of commercial and critical success. The band is active in human rights, international development, and social justice causes, such as Amnesty International, Make Poverty History, the ONE Campaign, Live Aid, Live 8, Bono's DATA (Debt, AIDS, Trade in Africa) campaign, and Music Rising.