"Waterloo" is the first single from ABBA's album Waterloo, which was their second album for Polar and their first for Epic and Atlantic. This was the song that won ABBA the 1974 Eurovision Song Contest and began their path to worldwide fame. The single was coupled with "Watch Out" as the B-side.
"Waterloo" was originally written as a song for the 1974 Eurovision Song Contest, after the group placed third with "Ring Ring" in the previous year's national heats. Since it focused on lead vocalists Frida Lyngstad and Agnetha Fältskog, Björn Ulvaeus and Benny Andersson chose it in place of another of their songs, "Hasta Mañana". It is about a girl who is about to surrender to romance, as Napoleon had to surrender at the Battle of Waterloo in 1815.
The song proved to be a good choice. It sailed through the Swedish heats (in Swedish) in February 1974 and won the 1974 Eurovision Song contest final on April 6 by six points.
"Waterloo" was one of ABBA's few songs to be written with simultaneous rock music and jazz beats, something later discarded in favor of more disco-esque rhythms.