Karl Duncker (2 February 1903, in Leipzig – 23 February 1940) was a German Gestalt psychologist. He attended Friedrich-Wilhelms-University from 1923 to 1923, and spent 1925–1926 at Clark University in Worcester, MA as a visiting professor, where he received a masters in arts degree. Until 1935 he was a student and assistant of the founders of Gestalt psychology in Berlin: Max Wertheimer, Wolfgang Köhler and Kurt Koffka.In 1935, exiled by the Nazis, he got an assistantship in Cambridge with Frederic Charles Bartlett and later immigrated to the US, where he was again an assistant of Wolfgang Köhler’s at Swarthmore College. He committed suicide in 1940 at 37 years of age. He had been suffering from depression for some time and had received professional treatment.