Simone de Beauvoir (1908-1986) was a French philosopher, writer, and feminist. She is best known for her 1949 book The Second Sex, which is considered a foundational text in the feminist movement. She was also a key figure in existentialism, a philosophical movement that focused on the individual's freedom of choice and responsibility for their actions. De Beauvoir wrote extensively on topics such as gender, sexuality, ethics, and politics. She was a vocal advocate for women's rights and was a major influence on the development of feminist thought. Her work continues to be widely read and studied today.