Mamma Mia
Written by Benny Andersson, Björn Ulvaeus, and Stig Anderson with lead vocals shared by Agnetha Fältskog and Anni-Frid Lyngstad, "Mamma Mia" was released in September 1975 as the sixth single from ABBA's self-titled third album. The song was ABBA's first number one in the UK since "Waterloo" in 1974.