Sigmund Freud's theories on the unconscious mind refer to the idea that much of human behavior is influenced by thoughts, feelings, and memories that lie outside of conscious awareness. Freud proposed that the unconscious is a reservoir of repressed desires and unresolved conflicts, playing a key role in shaping personality and influencing artistic expression. This concept became particularly significant in the context of early 20th-century movements like German Expressionism, where artists sought to tap into deeper emotional truths.