Sigmund Freud was the founder of psychoanalysis who introduced pioneering concepts such as the unconscious mind, dream analysis, and the significance of childhood experiences in shaping personality. His theories revolutionary challenged the understanding of human psychology, positing that much of our behavior is driven by unconscious motives and unresolved conflicts from early life. Freud’s work laid the foundation for various psychological theories and practices, influencing not just psychotherapy but also art, literature, and popular culture, providing a new lens through which to explore human behavior and mental processes.