Sigmund Freud (1856- 1939) was an Austrian neurologist and the founder of psychoanalysis. He is best known for his theories on the unconscious mind and the use of dream interpretation in psychoanalysis. Freud's work on the psyche has had a profound impact on psychology, literature, and popular culture. He wrote many books and essays during his lifetime, including The Interpretation of Dreams, which was published in 1899 and is considered a groundbreaking work in the field of psychology.