Simone de Beauvoir was a French philosopher, writer, and feminist born on January 9, 1908. She is best known for her influential work, "The Second Sex," published in 1949, which explores the construction of women's identity and the concept of gender. De Beauvoir's ideas contributed significantly to feminist theory and existentialism, emphasizing the importance of personal freedom and responsibility. In addition to her philosophical writings, de Beauvoir was a prominent figure in the existentialist movement, often associated with her partner, Jean-Paul Sartre. Throughout her life, she wrote novels, essays, and memoirs, addressing themes of ethics, politics, and the human condition. De Beauvoir passed away on April 14, 1986, leaving a lasting legacy in both philosophy and feminist thought.