"Unknown Song" is an instrumental track written and recorded by the British progressive rock group Pink Floyd. It has been released only on a bonus disc included in the 1997 re-release of the soundtrack to Michelangelo Antonioni's movie Zabriskie Point.

The track is simple and consists of melodies that were used later; the riff that starts to play at 1:54 is a faster tempo version of the "Mother Fore" section of "Atom Heart Mother Suite". The main melody played by acoustic 12-string guitar throughout the song is somewhat typical to the band's later style – "A Pillow of Winds" or even "Brain Damage" can be heard as followers of the song's melodies.

"Unknown Song" is sometimes called "Rain in the Country" or "Country Rain" on bootleg recordings. A similar piece entitled "Baby Blue Shuffle in D Major" appeared in a 2 December 1968 BBC radio broadcast and shared melodies with part one of "The Narrow Way" from Ummagumma, but it may have been rather a different – or even the same – take of "Unknown Song".

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