Simone Lucie Ernestine Marie Bertrand de Beauvoir (UK: , US: ; French: [simɔn də bovwaʁ] (listen); 9 January 1908 – 14 April 1986) was a French writer, intellectual, existentialist philosopher, political activist, feminist, and social theorist. Though she did not consider herself a philosopher, she had a significant influence on both feminist existentialism and feminist theory.Beauvoir wrote novels, essays, biographies, autobiographies and monographs on philosophy, politics, and social issues. She was known for her 1949 treatise The Second Sex, a detailed analysis of women's oppression and a foundational tract of contemporary feminism; and for her novels, including She Came to Stay and The Mandarins. Her most enduring contribution to literature is her memoirs, notably the first volume, “Mémoires d’une jeune fille rangée” (1958), which have a warmth and descriptive power. She was also known for her open, lifelong relationship with French philosopher Jean-Paul Sartre.