Björn Kristian Ulvaeus (Swedish pronunciation: , born 25 April 1945) is a Swedish musician, composer, a former member of the Swedish musical group ABBA (1972–82), and co-composer of the musicals Chess, Kristina från Duvemåla, and Mamma Mia!. He has recently coproduced the film Mamma Mia! with ex-ABBA member and close-friend Benny Andersson. During the last years Björn Ulvaeus has stepped forward as a frontline critic against the free file sharing of copyrighted material on the internet. He is also a prominent and outspoken member of the International Humanist and Ethical Union's Swedish member organisation Humanisterna.
Ulvaeus was born in Gothenburg, but as a child he moved with his family to Västervik. Ulvaeus studied business and law at Lund University after doing his military service with stand-up comedian Magnus Holmström.
Prior to gaining international recognition with ABBA, Björn was a member of the Swedish folk/schlager band Hootenanny Singers who had an enormous following in Scandinavia. While on the road in southern Sweden in 1966, they encountered the Hep Stars, and Björn quickly became friends with the group’s keyboard player, Benny Andersson. The two musicians shared a passion for songwriting, and each found a composing partner in the other. On meeting again that summer, they composed their first song together: "Isn't It Easy To Say"; a song soon to be recorded by Andersson's group. The two continued teaming up for music, helping out each other's bands in the recording studio, and adding guitar or keyboards respectively to the recordings. In 1968, they composed two songs together: "A Flower In My Garden", recorded by Hep Stars, and their first 'real' hit "Ljuva Sextiotal", for which Stig Anderson wrote lyrics. The latter - a cabarét-style ironic song about the 1960s - was submitted for the 1969 Swedish heats for Eurovision Song Contest, but was rejected; it was later recorded by diva Brita Borg. Another hit came in 1969 with "Speleman", also recorded by Hep Stars.