ABBA were the most commercially successful pop group of the 1970s, the origins of the Swedish superstars ABBA date way back to 1966, when keyboardist and vocalist Benny Andersson, a onetime member of the popular beat outfit the Hep Stars, first teamed with guitarist and vocalist Björn Ulvaeus, the leader of the folk-rock unit the Hootenanny Singers. The two performers began composing songs together and handling session and production work for Polar Music/Union Songs, a publishing company owned by Stig Anderson, himself a prolific songwriter throughout the 1950s and 1960s. At the same time, both Benny and Björn worked on projects with their respective girlfriends: Björn had become involved with vocalist Agnetha Fältskog, a performer with a recent number one Swedish hit, "I Was So in Love," under her belt, while Benny began seeing Anni-Frid Lyngstad, a one-time jazz singer who rose to fame by winning a national talent contest.

In 1971, Agnetha ventured into theatrical work, accepting the role of Mary Magdalene in a production of Andrew Lloyd Webber's Jesus Christ Superstar; her cover of the musical's "Don't Know How to Love Him" became a significant hit. The following year, the duo of Andersson and Ulvaeus scored a massive international hit with "People Need Love," which featured Agnetha and Frida on backing vocals. The record's success earned them an invitation to enter the Swedish leg of the 1973 Eurovision song contest, where, under the unwieldy name of Björn, Benny, Agnetha & Frida, they submitted "Ring Ring," which proved extremely popular with audiences but placed only third in the judges' ballots.

The next year, rechristened ABBA (a suggestion from Stig Anderson and an acronym of the members' first names), the quartet submitted the single "Waterloo," and became the first Swedish act to win the Eurovision competition. The record proved to be the first of many international hits, although the group hit a slump after their initial success as subsequent singles failed to chart. In 1975, however, ABBA issued "S.O.S.," a smash not only in America and Britain but also in non-English speaking countries such as Spain, Germany and the Benelux nations, where the group's success was fairly unprecedented. A string of hits followed, including "Mamma Mia," "Fernando," and "Dancing Queen" (ABBA's sole U.S. chart-topper), further honing their lush, buoyant sound; by the spring of 1976, they were already in position to issue their first Greatest Hits collection.

ABBA's popularity continued in 1977, when both "Knowing Me, Knowing You" and "The Name of the Game" dominated airwaves. The group also starred in the feature film ABBA -- The Movie, which was released in 1978. That year Benny and Frida married, as had Björn and Agnetha in 1971, although the latter couple separated a few months later; in fact, romantic suffering was the subject of many songs on the quartet's next LP, 1979's Voulez-Vous. Shortly after the release of 1980s Super Trouper, Benny and Frida divorced as well, further straining the group dynamic; The Visitors, issued the following year, was the final LP of new ABBA material, and the foursome disbanded after the December 1982 release of their single "Under Attack."

Although all of the group's members soon embarked on new projects -- both Frida and Agnetha issued solo LPs, while Benny and Björn collaborated with Tim Rice on the musical Chess -- none proved as successful as the group's earlier work, largely because throughout much of the world, especially Europe and Australia, the ABBA phenomenon never went away. Repackaged hits compilations and live collections continued hitting the charts long after the group's demise, and new artists regularly pointed to the quartet's inspiration: while the British dance duo Erasure released a covers collection, ABBA-esque, an Australian group called Björn Again found success as ABBA impersonators. In 1993, "Dancing Queen" became a staple of U2's "Zoo TV" tour -- Benny and Björn even joined the Irish superstars on-stage in Stockholm -- while the 1995 feature Muriel's Wedding, which won acclaim for its depiction of a lonely Australian girl who seeks refuge in ABBA's music, helped bring the group's work to the attention of a new generation of moviegoers and music fans.