Oswald Teichmüller, German mathematician (d. 1943)
Paul Julius Oswald Teichmüller (German: [ˈɔsvalt ˈtaɪçmʏlɐ]; 18 June 1913 – 11 September 1943) was a German mathematician who made contributions to complex analysis. He introduced quasiconformal mappings and differential geometric methods into the study of Riemann surfaces. Teichmüller spaces are named after him. He was also a committed Nazi.

Born in Nordhausen, Teichmüller attended the University of Göttingen, where he graduated in 1935 under the supervision of Helmut Hasse. His doctoral dissertation was on operator theory, though this was his only work on functional analysis. His next few papers were algebraic, but he switched his focus to complex analysis after attending lectures given by Rolf Nevanlinna. In 1937, he moved to the University of Berlin to work with Ludwig Bieberbach. Bieberbach was the editor of Deutsche Mathematik and much of Teichmüller's work was published in the journal, which made his papers hard to find in modern libraries before the release of his collected works.

A member of the Nazi Party (NSDAP) and Sturmabteilung (SA), the military wing of the NSDAP, from 1931, Teichmüller agitated against his Jewish professors Richard Courant and Edmund Landau in 1933. He was drafted into the Wehrmacht in July 1939 and took part in the invasion of Norway in 1940 before being recalled to Berlin to undertake cryptographic work with the Cipher Department of the High Command of the Wehrmacht. In 1942, he was released from his military duties and returned to teach at the University of Berlin. After the German defeat at Stalingrad in February 1943, he gave up his position in Berlin to volunteer for combat on the Eastern Front. He was killed in action in September 1943.

Sanford L. Segal, a professor of mathematics at the University of Rochester, in his 2003 book Mathematicians Under the Nazis said: "Teichmüller was a gifted, brilliant, and seminal mathematician; he was also a dedicated Nazi."