Wilhelm Emil "Willy" Messerschmitt (June 26, 1898 – September 15, 1978) was a German aircraft designer and manufacturer. He was born in Frankfurt am Main, the son of a wine merchant. His stepfather was the American painter and Munich Academy Professor Carl von Marr.

Probably Messerschmitt's single most important design was the Messerschmitt Bf 109, designed in 1934 with the collaboration of Walter Rethel. The Bf 109 became the most important fighter in the Luftwaffe as Germany re-armed prior to World War II. To this day, it remains the most produced fighter in history, with some 35,000 built. Another Messerschmitt aircraft, first called "Bf 109R", purpose built for record setting, but later re-designated Messerschmitt Me 209, broke the absolute world air speed record and held the world speed record for propeller-driven aircraft until 1969. His firm also produced the first jet-powered fighter to enter service — the Messerschmitt Me 262, although Messerschmitt himself did not design it.

As a young man, Messerschmitt befriended German sailplane pioneer Friedrich Harth. Harth joined the German army in 1914 and while he was away at war, Messerschmitt continued work on one of Harth's designs, the S5 glider. In 1917, Messerschmitt himself signed up for military service. Following the war, the two were re-united and continued to work together while Messerschmitt commenced study at the Munich Technical College and Harth built aircraft at the Bayerische Flugzeugwerke (BFW - Bavarian Aircraft Works). The S8 glider they designed and built together in 1921 broke a world duration record (albeit unofficially) and they went into partnership for a while running a flying school. The same year, the first plane entirely designed by Messerschmitt flew — the S9 glider.

During 1923 Harth and Messerschmitt had a falling out and went their separate ways, with Messerschmitt founding his own aircraft company at Augsburg. At first, Messerschmitt built sailplanes, but within two years had progressed via motor gliders to small powered aircraft - sports and touring types. These culminated in the Messerschmitt M17 and Messerschmitt M 18 designs, which Messerschmitt sold to BFW in 1927, when the Bavarian state government encouraged a merger between the two companies. These were followed by the Messerschmitt M20 light transport in 1928, which proved a disaster for BFW and Messerschmitt himself. Two Lufthansa M20s were involved in serious crashes very soon after purchase, and this led the airline to cancel their order for the type. This caused a serious cash-flow problem for the company and led to its bankruptcy in 1931. The M20 crashes also created a powerful enemy for Messerschmitt in the person of Erhard Milch, the head of Lufthansa who had lost a close friend in one of the crashes.

The establishment of the Reichsluftfahrtministerium ("Reich Aviation Ministry" - RLM) by the Nazi government in 1933, headed by Milch, led to a resurgence in the German aircraft industry and the resurrection of BFW. Collaborating with Robert Lusser, Messerschmitt designed the flagship product of the relaunched company, a low-wing sports monoplane called the Messerschmitt M37, but better known by its later RLM designation of Bf 108 Taifun. The following year, Messerschmitt would incorporate many design features of this aircraft into the Bf 109 fighter. Nevertheless, only the ties that Messerschmitt had formed with leading Nazis Rudolf Hess and Hermann Göring (through Theo Croneiss) saved him from sharing the fate of Milch's other great enemy, Hugo Junkers. To stay in business in the face of Milch ensuring that he would get no government contracts, Messerschmitt had signed agreements with Romania for sales of the M37 and a transport plane, the Messerschmitt M 36. When Milch learned of this, he publicly denounced Messerschmitt as a traitor, and the Gestapo was sent to question him and other BFW officials. Probably due to Croneiss' intervention, no further action was taken.

When in 1936, the Messerschmitt Bf 109 won the RLM's single-seat fighter contest to become one of the main Luftwaffe aircraft types, Messerschmitt and his factory took an important role in the RLM's armament plans, increasing in significance even further when Messerschmitt's Bf 110 also won the multi-purpose fighter contest.

On July 11, 1938, Messerschmitt was appointed chairman and managing director of Bayerische Flugzeugwerke and the company was renamed after him to Messerschmitt AG. This same year, the company began work on what would eventually become the Me 262, and of the Messerschmitt Me 210, planned as successor for the Bf 110. The Me 210 turned out to be plagued by massive development problems that were only solved by evolving the type into the Messerschmitt Me 410, and the resulting problems and delays again put the reputation of both Messerschmitt and his namesake company in jeopardy.

Following World War II, Messerschmitt was tried by a denazification court for using slave labor, and in 1948 was convicted of being a "fellow traveller". After two years in prison, he was released and resumed his position as head of his company. Since Germany was forbidden to manufacture aircraft until 1955, he turned his company to manufacturing prefabricated buildings, sewing machines, and small cars - most notably the Messerschmitt Kabinenroller. Exporting his talents, he designed the Hispano HA-200 jet trainer for Hispano Aviacion in Spain in 1952 before eventually being allowed to return to aircraft manufacturing in Germany to licence-produce the Fiat G91 and then Lockheed F-104 Starfighter for the West German Luftwaffe. He designed the later Helwan HA-300 supersonic interceptor.

Messerschmitt saw his company through mergers first with Bölkow in 1968 and then Hamburger Flugzeugbau in 1969, at which point it became MBB (Messerschmitt-Bölkow-Blohm, now part of EADS) with Messerschmitt as chairman until 1970 when he retired. He died eight years later in hospital in Munich.

Messerschmitt's designs were characterized by a clear focus on performance, especially by striving for lightweight construction, but also by minimizing parasitic drag from aerodynamic surfaces. His critics accused him of taking this approach too far in some designs. His falling out with Harth had been over designs Harth felt to be dangerously unstable, and the Me 210 displayed instability, too, which could only be cured by enlarging the airframe and the aerodynamic surfaces, increasing drag and weight. Messerschmitt's design philosophy also is evident in his arguments with Alexander Lippisch, who was designing the tailless Me 163 rocket fighter for production at the Messerschmitt works. While Lippisch maintained the tailless design on principle had an advantage with regard to total drag, Messerschmitt pointed out that the design compromises necessary to make a tailless aircraft safely controllable defeated this purpose by increasing drag to the original level and above.

Messerschmitt was appointed an Honorary Professor by the Munich Technical College in 1930, and the Vice-President of the Deutsche Akademie für Luftfahrtforschnung (German Academy of Aeronautical Research). The German government also awarded him the title of Wehrwirtschaftsführer (defense industry leader). In 1938, Adolf Hitler bestowed upon Messerschmitt the German National Prize for Art and Science.