Björn Ulvaeus

Björn Kristian Ulvaeus (born 25 April 1945) is a Swedish musician, singer, songwriter, and producer best known as a member of the musical group ABBA. He is also the co-composer of the musicals Chess, Kristina från Duvemåla, and Mamma Mia! He co-produced the films Mamma Mia! and Mamma Mia! Here We Go Again with fellow ABBA member and close friend Benny Andersson.

He is the oldest member of the group. Björn Kristian Ulvaeus was born in Gothenburg on 25 April 1945. In 1951, he moved with his family to Västervik, Kalmar County. His parents were Aina Eliza Viktoria (née Bengtsson; 1909–2005) and Erik Gunnar Ulvaeus (1912–1999). Ulvaeus has one sister, Eva Margareta (born 1948).

Ulvaeus studied business and law at Lund University after undertaking his military service, alongside comedian Magnus Holmström. Before gaining international recognition with ABBA, Ulvaeus was a member of the Swedish folk-schlager band Hootenanny Singers, known earlier as the "West Bay Singers", who had an enormous following in Scandinavia. While on the road in southern Sweden in 1966, they encountered the Hep Stars, and Ulvaeus 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.