"Fat Old Sun" is a Pink Floyd song written and sung by David Gilmour. It appears on their 1970 album Atom Heart Mother, and was performed live in a greatly expanded form (often exceeding fourteen minutes), both before and after the album was released (10 October). Live performances of this song date back to 16 July 1970.
"Fat Old Sun" was performed live by Pink Floyd from 1970–71. On stage, the song was transformed from a folk ballad into an extended progressive rock jam, leading off from the blues rock solo after the last refrain. Extended jams would usually follow, including free-form drumming, organ solos and revised chord progressions based on the "Sing to me" vocal line.
More recently, it was adopted by David Gilmour and performed acoustically in the 2001/02 David Gilmour in Concert shows, minus the electric guitar solo. When the Floyd's manager, Steve O'Rourke, died in 2003, Gilmour, Richard Wright, and Nick Mason played "Fat Old Sun" and "The Great Gig in the Sky" at O'Rourke's funeral. Early during the tour in support of Gilmour's On an Island album in 2006, the song returned to the set list. This incarnation was composed of the lyrics followed by the concert's backing singers repeating the "sing to me" chorus, then a bluesy version of the guitar solo closer to the length of the album version (the 2006 incarnation clocked in at around seven minutes). A performance from the Royal Albert Hall is featured on Gilmour's DVD, Remember That Night. It is also featured on Gilmour's live album Live in Gdańsk.