Sigmund Freud (1856–1939) was a Viennese neurologist who became one of the most influential figures of the twentieth century. As the inventor of psychoanalysis, he introduced concepts of the unconscious, the impact of childhood, repressed emotions, and even the entire field of psychotherapy to the wider world. While aspects of his theories remain controversial, much of his work has become such an integral part of our culture that it is taken for granted.