Arguably the most famous of all World War II aircraft, the Supermarine Spitfire was designed by famed British aircraft designer R. J. Mitchell from the successful Supermarine seaplanes of the 1930s. The Spitfire was characterized by elegant, attractive lines, and an innovative elliptical wing. In later marks, the wingtips (typically rounded) were removable and fitted according to the aircraft's role: clipped for low-level operations and pointed for high-altitude combat. The wings had provisions for a variety of cannon and machine gun configurations, as well as bombs in later versions. Visibility was also noticeably improved from other contemporary fighters by the use of a bulged Malcolm hood; late-war Spitfires were fitted with bubble hoods as well. The excellent flight characteristics and maneuverability of the prototypes led to immediate production from 1938, becoming the RAF's finest fighter at the beginning of the war. The Spitfire's definitive claim to fame came during the Battle of Britain when alongside the Hurricane it shared the lion's burden of defending the British Isles against the Luftwaffe assault. Although not flown with as many units as the Hurricane, the Spitfire proved to be a match for the German Bf 109 against which it boasted higher maneuverability. It later began making fighter-sweeps over occupied Europe and as new types of German aircraft began entering service (notably the Fw 190), the Spitfire proved its versatility by being constantly refined and upgraded to the point that it never ceased to be a match against any other enemy fighter over Europe. By the end of the war, Spitfires were used to take on German jet fighters and V-1 flying bombs, and it was also used for many other roles including photo-reconnaissance and ground attack. Perhaps its only major drawback was a lack of range, at least compared to late-war US fighters such as the P-47 and P-51; as such it played a more modest role in the destruction of the Luftwaffe from 1944 onward although it retained its value as the mainstay of the Allies' tactical fighter force. Over 30 countries operated the Spitfire including wartime use by Australia, Canada, Egypt, France, Greece, Italy, New Zealand, Portugal, South Africa Turkey, the USA, and the USSR. Production continued into 1946 and its service record with the RAF ended only in the mid-1950s, becoming not just one of the finest examples of British engineering but a strong candidate for the title of the greatest combat aircraft in history.

The Spitfire was first flown in prototype form on 5 March 1936 entering service in June 1938. The Spitfire Mk. I was the principal variant used during the Battle of Britain, equipping no less than 19 squadrons. The Mk. II was generally similar except for slightly improved powerplant and armor protection and also participated in the latter stages of the battle. The next mayor variant, the Mk. V, was used extensively for fighter sweeps over occupied Europe as well as in North Africa where it was usually accommodated with a sand filter under the nose; it was to become the most widely produced Spitfire variant of all. Nevertheless, Mk Vs were soon outclassed by the new Fw 190A during 1941-1942 and it was only with the hurried introduction of the superb Mk. IX that the odds were evened. The Mk. IX was the first Spitfire variant to exceed 400 mph and represented the pinnacle of Spitfire design with the Rolls-Royce Merlin engine. Subsequently, some Spitfires were optimized for high-altitude performance, this began with the Mk. VI and continued with the Mk. VII which featured a pressurized cockpit. The Mk. VIII was similar but unpressurized and was originally slated to be the successor to the Mk. V but delays resulted in the Mk. IX being rushed into service first. As a result, it was designed fully tropicalized for service in the Mediterranean and the Far East. The Mk. VII-IXs came in various sub-variants optimized for different altitudes which were differentiated by the type of Merlin engine they were equipped with. These were designated with either a LF (low-altitude), HF (high-altitude) or F (standard) prefix. A final development of the Merlin-powered Spitfire was the Mk. XVI, although its engines were license-built in the US by Packard. As was the norm with most late-war Spitfires, it came in both normal high-back and low-back versions, the latter with a bubble canopy for increased visibility. Most also had clipped wings. Having reached the limits of the Merlin's capability, the next major redesign of the Spitfire involved use of the larger and more powerful Griffon engine. The first Griffon variant was the Mk. XII and was followed by the Mk. XIV which became the finest Spitfire variant of the war, capable of taking on the latest German fighters like the Fw 190D and even the jet-powered Me 262 (A Mk. XIV was the first allied aircraft to shoot one down). Due to their speed, they were also used extensively against V-1 bombs and over 300 of these were successfully intercepted. Like the Mk. XVI, the Mk. XIV was frequently seen with clipped wings for low-level operations and many were fitted with bubble canopies too. The Spitfire was also a very useful photographic aircraft, and variants which served for this role were the PR.X, PR.XI, and PR.XIX which were unarmed, in addition to conversions from other marks (plus fighter-recon versions like the FR.XIV). Final variants include the Mk. XVIII, as well as the F.21, F.22 and F.24, the later three which were fitted with a redesigned wing as well as other structural changes. Of these, only the F.21 saw some action in the final stages of the war. Navalized variants were designated Seafire and served aboard Royal Navy carriers up to the Korean War, these are covered in a separate entry.