<p>The existentialism of Sartre and Beauvoir presents us with a puzzle: on one hand, all values depend on our free choices. On the other hand, one value—freedom—seems to be normatively binding on all agents. In this paper I aim to resolve the puzzle through a reconstruction of the ethics of Sartre and especially Beauvoir as versions of constitutivism. Constitutivism holds that agency has some constitutive aim(s) and that norms derived from such aims are therefore binding on all agents. I argue that Sartre can be read, and Beauvoir should be read, as a constitutivist: free agency necessarily aims at freedom, and this means that as agents we necessarily aim to expand rather than constrict freedom, whether in ourselves or others. After presenting the core argument supporting Beauvoir’s conclusion, I proceed to respond to two sorts of objections to Beauvoirean constitutivism. The first claims that if the aim of freedom is constitutive of agency, it is impossible to fail to pursue the aim. The second claims that Beauvoir can at best give us a purely subjectivist ethics. I argue that Beauvoir has a well-developed account of how agents can deviate from the aim of freedom, and there are both textual and theoretical reasons why her appeal to an objective value should manifest itself as subjectivism.</p>