ABBA ( AB-ə [ˈâbːa]) were a Swedish pop group formed in Stockholm in 1972 by Agnetha Fältskog, Björn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad. They are among the most renowned and commercially successful musical groups in history, ranking as one of the best-selling music acts in the history of popular music.

In 1974, ABBA became Sweden's first winner of the Eurovision Song Contest with the song "Waterloo", which in 2005 was chosen as the best song in the competition's history as part of the 50th anniversary celebration of the contest. During the band's main active years, it consisted of two couples: Fältskog and Ulvaeus, and Lyngstad and Andersson. With the increase of their popularity, their personal lives suffered, which eventually resulted in the collapse of both marriages. The relationship changes were reflected in the group's music, with later songs featuring darker and more introspective lyrics. After ABBA disbanded in December 1982, Andersson and Ulvaeus continued their success writing music for multiple audiences including stage, musicals and movies, while Fältskog and Lyngstad pursued solo careers. Ten years after the group broke up, a compilation, ABBA Gold, was released, becoming a worldwide best-seller. In 1999, ABBA's music was adapted into Mamma Mia!, a stage musical that toured worldwide and, as of October 2024, is still in the top-ten longest running productions on both Broadway (closed in 2015) and the West End (still running). A film of the same name, released in 2008, became the highest-grossing film in the United Kingdom that year.