Ernst Rüdin (April 19, 1874 in St. Gallen – October 22, 1952) was a Swiss-born German psychiatrist, geneticist, eugenicist and Nazi. Rising to prominence under Emil Kraepelin and assuming his directorship at what is now called the Max Planck Institute of Psychiatry in Munich. While he has been credited as a pioneer of psychiatric inheritance studies, he also argued for, designed, justified and funded the mass sterilization and clinical killing of adults and children.