Karen Horney was a pioneering German psychoanalyst known for her theories on neurosis, feminine psychology, and self psychology, challenging many of Sigmund Freud's ideas. She identified ten neuroses and contributed significantly to understanding the psychological treatment of women, advocating that gender differences stem from cultural and socialization influences rather than biology. Horney's legacy includes teaching at various institutes and founding the American Institute for Psychoanalysis, influencing numerous fields in psychology.