The Waterloo Singers are a Swedish pop group formed in 1972. They are best known for their hit single 'ABBA', which was released in 1974 and reached number one on the charts in several countries. The group consists of four members: Agnetha Fältskog, Björn Ulvaeus, Benny Andersson, and Anni-Frid Lyngstad. They have sold over 380 million records worldwide, making them one of the best-selling music artists of all time.