Successive generations of scholars have been hugely effective at challenging the once-common dismissal of Beauvoir's philosophy and the view that her work was a mere application of “Sartre's existentialism”. But while the originality and significance of Beauvoir's philosophical contributions are now widely acknowledged, there remains a series of foundational debates concerning The Second Sex and the precise nature of Beauvoir's intellectual relationship with Sartre. Although there is little consensus on this last point, it is increasingly common for scholars to distance Beauvoir's feminism from Sartre's early existentialism, especially his theory of existential freedom in Being and Nothingness. This partially derives from an enduring and widespread consensus that Sartre's early theory of freedom is fundamentally insensitive to the empirical realities of oppressive situations and therefore inimical to feminism.In this paper, I argue that the essence of Beauvoir's theory of freedom in The Second Sex is broadly consistent with Sartre's in Being and Nothingness, but that Beauvoir makes some major advances on Sartre by properly developing the relationship between freedom and power, resulting in a compelling existentialist framework for agency that significantly increases the viability of existentialism as a normative philosophy. I aim to demonstrate that recognising the foundational consistencies between Beauvoir's philosophy and Sartre's existentialism by no means detracts from Beauvoir's originality and intellectual independence, but rather champions it by allowing us to appreciate some of the most original and insightful features of The Second Sex and its role in the development of existentialism.