Authenticity has been conceived of in several different ways with various meanings and implications. The existential conception has the advantage of tracking authenticity from the phenomenology of human beings and their lived, social experience. From Jean-Paul Sartre and Martin Heidegger’s criteria for existentialist authenticity, I develop the argument that authentic, feminist projects are necessarily one mode of being authentic within a patriarchal society. In defining a conception of authenticity out of Sartre and Heidegger’s terms, the question of what qualifies as an authentic feminist project arises as well as the question of what sort of content qualifies as authentic. While Simone De Beauvoir does not focus on authenticity in her ethics, she does give a basis for a value oriented, content relevant aspect of existentialism generally. Insofar as authenticity is an existentialist concept, feminist authenticity is one valuable and worthwhile project within a social patriarchy, as it promotes existence as freedom.