Dating from her years as a philosophy student at the Sorbonne, this is the 1926-27 diary of the teenager who would become the famous French philosopher, author, and feminist, Simone de Beauvoir. Written years before her first meeting with Jean-Paul Sartre, these diaries reveal previously unknown details about her life and offer critical insights into her early philosophy and literary works. Presented here for the first time in translation and fully annotated, the diary is completed by essays from Barbara Klaw and Margaret A. Simons that address its philosophical, historical and literary significance. The volume represents an invaluable resource for tracing the development of Beauvoir's independent thinking and influence on the world.