Simone Lucie Ernestine Marie Bertrand de Beauvoir (9 January 1908 – 14 April 1986) was a French author and existentialist philosopher. She is now most famous for her 1949 treatise The Second Sex [Le Deuxième Sexe], a detailed analysis of women's oppression and a foundational tract of contemporary feminism, and her long personal relationship with Jean-Paul Sartre.