Karl Leonhard (21 March 1904 – 23 April 1988) was a German psychiatrist who was a student and collaborator of Karl Kleist, who himself stood in the tradition of Carl Wernicke.
With Kleist, he created a complex classification of psychotic illnesses called Nosology.
His work covered psychology, psychotherapy, biological psychiatry and biological psychology.
Moreover, he created a classification of nonverbal communication.