Stefan or Stephan Cohn-Vossen (28 May 1902 – 25 June 1936) was a mathematician, now best known for his collaboration with David Hilbert on the 1932 book Anschauliche Geometrie, translated into English as Geometry and the Imagination[1]. The Cohn-Vossen transformation is also named for him[2].
He was born in Breslau (now Wrocław in Poland). He wrote a 1924 doctoral dissertation at the University of Wrocław. He became a professor at the University of Cologne in 1930.
He was barred from lecturing in 1933 under Nazi racial legislation, because he was Jewish. In 1934 he emigrated to the USSR, with some help from Herman Müntz. While there, he taught at Leningrad University. He died in Moscow from pneumonia.