Sigmund Freud is known as the father of psychoanalysis. He developed this field in the late 19th and early 20th centuries, focusing on the unconscious mind, repressed thoughts, and early childhood experiences. Freud's theories introduced concepts such as the id, ego, and superego, which describe the structures of personality. His work laid the groundwork for various forms of psychotherapy and influenced numerous disciplines, including literature, art, and philosophy. Despite controversies surrounding his methods and ideas, Freud’s contributions remain foundational in understanding human behavior and mental processes.