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.