Simone de Beauvoir was a French writer, philosopher, political activist, and social theorist. She is best known for her 1949 treatise 'The Second Sex', a detailed analysis of women's oppression and a foundational tract of contemporary feminism. De Beauvoir also wrote novels, essays, biographies, and monographs on philosophy, politics, and social issues. She is often referred to as one of the leading figures of existentialism and feminism.