The WATERLOO Quartet is a Swedish pop group best known for their hit song 'WATERLOO, ' which won the 1974 Eurovision Song Contest. The quartet consists of Benny Andersson, Björn Ulvaeus, Agnetha Fältskog, and Anni-Frid Lyngstad, who are collectively known as ABBA. The group was formed in 1972 and went on to become one of the most successful musical acts of the 1970s and 1980s. They have sold over 380 million records worldwide, making them one of the best-selling music artists of all time.