Simone de Beauvoir is one of the best-known philosophers of the 20th century. At least her name is recognizable, even though her actual work may not be. She is credited with originating the concept of “the other” before Sartre, her life companion, used it. Her philosophical works make use of literary works and de Beauvoir herself wrote novels in addition to philosophical works and to make philosophical ideas more accessible. Perhaps she is best known for “The Second Sex” which she published in 1949, about the condition of women. This is a pivotal work in 20th century feminism, and despite some limitations, survives the test of time. She also wrote several philosophical treatises and was one of the contributors to the development of existentialism, the prevalent philosophical current after WWII. Later in her life she wrote about aging and participated actively in the French feminist political movement until her death. In this presentation we will look at her life and theoretical and feminist contributions to 20th century thought.