Gaetano Kanizsa (Trieste, 1913 – 1993) was an Italian psychologist of Jewish and Slovene descent who also worked as a painter. He is best known for his research on visual perception, although his painting ran alongside his scientific work throughout his life.
Born in Trieste, then part of Austria-Hungary, he took his degree at the University of Padua in 1938 with a thesis on eidetic memory. After a post as teaching assistant at the University of Florence, he returned to Trieste in 1953 as full professor, a chair he held for thirty years. He retired from academic life in 1988 and kept researching until his death in 1993. He was one of the founders of the Institute of Psychology in Trieste.
In the 1970s he became famous after a 1976 article on illusory contours in Scientific American and the 1979 book Organization in Vision. The figure in which three illusory contours form a triangle is known as the Kanizsa triangle, and it shows how the brain completes shapes that are not actually drawn. He is regarded as a dominant figure in Italian psychology.