The Supermarine Spitfire is a British single-seat fighter aircraft that was used by the Royal Air Force and many other Allied countries throughout the Second World War. The Spitfire continued to be used as a front line fighter and in secondary roles into the 1950s. It was produced in greater numbers than any other British aircraft and was the only British fighter in production throughout the war.

The Spitfire was designed as a short-range, high-performance interceptor aircraft by R. J. Mitchell, chief designer at Supermarine Aviation Works (which operated as a subsidiary of Vickers-Armstrong since 1928). Mitchell continued to refine the design until his death from cancer in 1937, whereupon his colleague Joseph Smith became chief designer. The Spitfire's elliptical wing had a thin cross-section, allowing a higher top speed than several contemporary fighters, including the Hawker Hurricane. Speed was seen as essential to carry out the mission of home defence against enemy bombers.

During the Battle of Britain (July-October 1940), the Spitfire was perceived by the public as the RAF fighter of the battle, though the more numerous Hawker Hurricane shouldered a greater proportion of the burden against the Luftwaffe. The Spitfire units had a lower attrition rate and a higher victory to loss ratio than those flying Hurricanes.