Sigmund Freud, an Austrian neurologist born in 1856, significantly influenced psychology through his exploration of the unconscious mind. His interest in patients suffering from hysteria and neurosis — conditions without apparent physical causes — led him to theorize the existence of an unconscious mind, a repository for feelings and urges beyond our awareness. Freud's innovative approach included techniques such as dream analysis, free association, and attention to slips of the tongue to access the unconscious.

Freud posited that early childhood experiences heavily influence personality development and mental health. His psychoanalytic theory emphasized the role of unconscious processes and early experiences in shaping behavior and psychological issues. Despite controversies surrounding some of his ideas, Freud's contributions have been foundational, influencing various fields within psychology, including therapy, personality, and developmental studies.

Freud's legacy includes the concept of psychoanalysis, a therapeutic method focused on uncovering and understanding unconscious motivations and conflicts. This approach has evolved and remains a part of modern psychological practice, with evidence supporting its effectiveness. Freud's work sparked a broader discussion about the mind's complexities, leading to subsequent theories and practices that continue to enrich psychology.

His influence extends through his followers, including notable figures like Alfred Adler, Carl Jung, and Anna Freud, who expanded upon his ideas and contributed their perspectives to the field. Despite the evolution of psychology and the emergence of new theories and approaches, Freud's foundational concepts, particularly regarding the unconscious mind and the importance of early experiences, continue to inform and provoke debate within the discipline.