No. 631 Squadron RAF was an anti-aircraft co-operation squadron of the Royal Air Force from 1943 to 1949.
The squadron was formed at RAF Towyn on 1 December 1943, from 1605 Flight and 1628 Flight for anti-aircraft co-operation duties, and operated a variety of aircraft in this role. On 10 May 1945 the squadron moved to RAF Llanbedr. It was disbanded on 11 February 1949 when redesignated No. 20 Squadron RAF.
- Bowyer, Michael J.F. and John D.R. Rawlings. Squadron Codes, 1937-56. Cambridge, UK: Patrick Stephens Ltd., 1979. ISBN 0-85059-364-6.
- Delve, Ken. The Source Book of the RAF. Shrewsbury, Shropshire, UK: Airlife Publishing, 1994. ISBN 1-85310-451-5.
- Flintham, Vic and Andrew Thomas. Combat Codes: A full explanation and listing of British, Commonwealth and Allied air force unit codes since 1938. Shrewsbury, Shropshire, UK: Airlife Publishing Ltd., 2003. ISBN 1-84037-281-8.
- Halley, James J. The Squadrons of the Royal Air Force & Commonwealth 1918-1988. Tonbridge, Kent, UK: Air Britain (Historians) Ltd., 1988. ISBN 0-85130-164-9.
- Jefford, Wing Commander C.G., MBE, BA, RAF (Retd). RAF Squadrons, a Comprehensive Record of the Movement and Equipment of all RAF Squadrons and their Antecedents since 1912. Shrewsbury, Shropshire, UK: Airlife Publishing, 2001. ISBN 1-84037-141-2.
- Rawlings, John D.R. Coastal, Support and Special Squadrons of the RAF and their Aircraft. London: Jane's Publishing Company Ltd., 1982. ISBN 0-7106-0187-5.