No. 21 Group RAF is a former Royal Air Force group that existed from April-July 1918; 1926-1934, a redesignation of No. 1 Group RAF; after which it was merged into ; and from 1938 to 1955. The group was transferred to Flying Training Command on 27 May 1940, responsible for the RAF College and the Service Flying Training Schools from the Midlands northwards. On 1 May 1947, the Group absorbed No. 91 Group RAF, of Bomber Command, taking over HQ No. 91 Group, Morton Hall, Swinderby. On 24 June 1953 the Group absorbed , which had been reformed 22 months earlier within Flying Training Command to control Initial Training Wings and Grading Schools. No. 21 Group disbanded on 1 March 1955.