Reginald Joseph Mitchell CBE, FRAeS, (20 May 1895 – 11 June 1937) was a British aeronautical engineer, working for Supermarine and then Vickers. Between 1920 and 1936 he designed many aircraft, including light aircraft, fighters, bombers and flying boats. He is best remembered for his work on a series of racing aircraft, which culminated in the Supermarine S.6B and an iconic Second World War fighter - the Supermarine Spitfire.

The technical skill that led ultimately to the design of the Spitfire was developed through the experience RJ Mitchell and his team gained in the evolution of the Schneider Trophy seaplanes. The significance of the many earlier planes is often overlooked when people refer to RJ Mitchell, as is the fact that as a man he was very concerned about developments in Germany and feared that British defence needed to be strengthened, especially in the air.

In 1931 the Air Ministry issued specification F7/30 for a fighter aircraft to replace the Gloster Gauntlet. Mitchell's proposed design, the Type 224 was one of three designs for which the Air Ministry ordered prototypes.

It first flew on 19 February 1934, but was eventually rejected by the RAF because of its unsatisfactory performance. While the 224 was being built, Mitchell was authorised by Supermarine in 1933 to proceed with a new design, the Type 300, an all-metal monoplane that would become the Supermarine Spitfire. This was originally a private venture by Supermarine, but the RAF quickly became interested and the Air Ministry financed a prototype.

Many of the technical advances in the Spitfire had been made by others: the thin elliptical wings were designed by the Canadian aerodynamicist, Beverley Shenstone, and shared some similarities with the Heinkel He 70 Blitz; the under-wing radiators had been designed by the RAE, while monocoque construction had been first developed in the United States. Mitchell's genius was bringing it all together with his experience of high speed flight and the Type 224.

The first prototype Spitfire, serial K5054, flew for the first time on 5 March 1936 at Eastleigh, Hampshire. In later tests, it reached 349 mph, consequently, before the prototype had completed its official trials, the RAF ordered 310 production Spitfires. Mitchell is reported to have said that "Spitfire was just the sort of bloody silly name they would choose."

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