Simone de Beauvoir was a French writer, philosopher, political activist, and feminist. She is best known for her 1949 treatise 'The Second Sex', which is considered a foundational text of contemporary feminism. She was also a close friend and lifelong companion of Jean-Paul Sartre, with whom she wrote books, essays, and plays. They were both part of the existentialist movement, and their relationship was often referred to as 'the couple'. De Beauvoir's nickname was 'Simone' and her close friends called her 'Amie'.