The theory of psychoanalysis was developed by Sigmund Freud, an Austrian neurologist. Freud introduced psychoanalysis in the late 19th century as a method for treating mental illness and a theory of human psychology. His work emphasized the importance of the unconscious mind, repressed feelings, and childhood experiences in shaping behavior and personality. Freud's ideas, such as the Oedipus complex, dream analysis, and free association, revolutionized psychology and influenced various fields, including literature, art, and philosophy. Despite facing criticism and evolving viewpoints, Freud's contributions remain foundational in understanding human behavior and therapeutic practices.