Björn Kristian Ulvaeus (Swedish: [ˈbjœːɳ ɵlˈvěːɵs] ; 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...