The Supermarine Spitfire is a British single-seat fighter aircraft used by the Royal Air Force and many other Allied countries through the Second World War and on into the 1950s as a front line fighter and in secondary roles. It was produced in greater numbers than any other Allied fighter design (the Russian Ilyushin Il-2/Il-10 series of ground-attack aircraft was produced in greater quantity). The Spitfire was the only Allied fighter in production throughout the Second World War.

The Spitfire was designed by R. J. Mitchell, chief designer at Supermarine Aviation Works, since 1928 a subsidiary of Vickers-Armstrongs. He continued to refine the design until his death from cancer in 1937, whereupon his colleague Joseph Smith became chief designer. Its elliptical wing had a thin cross-section, allowing a higher top speed than the Hawker Hurricane and many other contemporary designs.

The distinctive silhouette imparted by the wing planform helped the Spitfire to achieve legendary status during the Battle of Britain. There was, and still is, a public perception that it was the RAF fighter of the Battle although the more numerous Hurricane actually shouldered a greater proportion of the burden against the potent Luftwaffe.

After the Battle of Britain the Spitfire became the backbone of RAF Fighter Command and saw action in the European Theatre, Pacific Theatre and the South-East Asian theatre. Much loved by its pilots, the Spitfire saw service in several roles and was built in many different variants.

The Spitfire will always be compared to its main adversary, the Messerschmitt Bf 109: both were among the finest fighters of their day and followed similar design philosophies of marrying a small, streamlined airframe to a powerful liquid-cooled V12 engine.

Design and development

R. J. Mitchell's 1931 design to meet Air Ministry specification F7/30 for a new and modern fighter capable of , the Supermarine Type 224, resulted in an open-cockpit monoplane with bulky gull-wings and a large fixed, spatted undercarriage powered by the evaporative-cooled Rolls-Royce Goshawk engine. This made its first flight in February 1934. Andrews and Morgan 1987, p. 206. This aircraft was a big disappointment to Mitchell and his design team, who immediately embarked on a series of "cleaned-up" designs, using their experience with the Schneider Trophy seaplanes as a starting point. The F7/30 design accepted was the Gloster Gladiator biplane.Price 1977, p. 16.

Mitchell had already begun working on a new aircraft, designated Type 300, based on the Type 224. With a retractable gear and the wingspan reduced by , the aircraft was submitted to the Air Ministry in July 1934, but again was not accepted. The design evolved through a number of changes, including an enclosed cockpit, oxygen-breathing apparatus, even smaller and thinner wings, and the newly-developed and much more powerful Rolls-Royce PV-XII V-12 engine, later named the Merlin. In November 1934, Mitchell, with the backing of Supermarine's owner, Vickers-Armstrongs, started detailed design work on the Type 300. The Air Ministry issued a contract AM 361140/34 on 1 December 1934, providing £10,000 for the construction of Mitchell's "improved F7/30 design". Price 1977, p. 20. On 3 January 1935, the Air Ministry formalised the contract and a new Specification F10/35 was written around the aircraft.