Day-O (The Banana Boat Song)" is a traditional Jamaican folk song. The song has mento influences, but it is commonly classified as an example of the better known calypso music.

It is a work song, from the point of view of dock workers working the night shift loading bananas onto ships. The lyrics describe how daylight has come, their shift is over, and they want their work to be counted up so that they can go home.

The best-known version was released by American singer Harry Belafonte in 1956 and later became one of his signature songs. That same year The Tarriers released an alternative version that incorporated the chorus of another Jamaican folk song, "Hill and Gully Rider". The Tarriers version was recorded by Shirley Bassey in 1957 for her 1959 album The Bewitching Miss Bassey.

The song was first recorded by Trinidadian singer Edric Connor and his band "Edric Connor and the Caribbeans" on the 1952 album Songs From Jamaica; the song was called "Day Dah Ligh Belafonte based his version on Connor's 1952 and Louise Bennett's 1954 recordings.

In 1955, American singer-songwriters Lord Burgess and William Attaway wrote a version of the lyrics for the Colgate Comedy Hour, in which the song was performed by Harry Belafonte. Belafonte recorded the song for RCA Victor and this is the version that is best known to listeners today, as it reached number five on the Billboard charts in 1957 and later became Belafonte's signature song. Side two of Belafonte's 1956 Calypso album opens with "Star O", a song referring to the day shift ending when the first star is seen in the sky. During recording, when asked for its title, Harry spells, "Day Done Light".

Also in 1956, folk singer Bob Gibson, who had traveled to Jamaica and heard the song, taught his version to the folk band The Tarriers. They recorded a version of that song that incorporated the chorus of "Hill and Gully Rider", another Jamaican folk song. This release became their biggest hit, reaching number four on the pop charts, where it outperformed Belafonte's version. The Tarriers' version was recorded by Shirley Bassey in 1957 and it became a hit in the United Kingdom. The Tarriers, or some subset of the three members of the group (Erik Darling, Bob Carey and Alan Arkin, later better known as an actor) are sometimes credited as the writers of the song; their version combined elements of another song and was thus newly created.