Sigmund Freud (1856–1939) was an Austrian neurologist and the founder of psychoanalysis, one of the most influential intellectual movements of the 20th century. Born in what is now the Czech Republic, Freud developed a revolutionary model of the human psyche, proposing that unconscious drives, particularly those related to sexuality and aggression, shape behavior and mental life. In Five Lectures on Psycho-Analysis, delivered in 1909 at Clark University in the United States, Freud offered a clear and concise introduction to his theories of repression, dream interpretation, the Oedipus complex, and the structure of the unconscious. These lectures marked his first major appearance on the international stage and introduced psychoanalysis to a broader audience. Freud's legacy is complex—simultaneously lauded for transforming psychology and critiqued for methodological and cultural biases. Nonetheless, his work laid the groundwork for psychotherapy, modern psychiatry, and vast swaths of 20th-century literature, art, and critical theory.