Roger Keith "Syd" Barrett (6 January 1946 – 7 July 2006), was an English singer-songwriter, guitarist, and painter, best remembered as a founder member of the band Pink Floyd. He was the lead vocalist, guitarist and primary songwriter during the band's psychedelic years, providing major musical and stylistic direction in their early work, including their name. He left the group in 1968 amid speculations of mental illness exacerbated by drug use, and was briefly hospitalised.

Besides being a pioneer in psychedelic rock with his expressive guitar playing and imaginative compositions, Barrett was also a pioneer in the space rock and psychedelic folk genres. He was active in music for only about seven years, recording four singles, the debut album (and contributed to the second one), plus several unreleased songs with Pink Floyd; and a single and two albums (plus a third one of unreleased tracks/alternate takes), as a solo musician, before going into self-imposed seclusion lasting more than thirty years.

In his post-musician life, he continued with his painting and dedicated himself to gardening, never to return to the public eye. He died in 2006. A number of biographies have been written about him since the 1980s, and Pink Floyd wrote and recorded several tributes to him after he left, most notably the 1975 album Wish You Were Here.