This paper explores the theory of freedom that Emilie du Châtelet advances in her essay "On Freedom." Using contemporary terminology, we can characterize this theory as a version of agent-causal compatibilism. More specifically, the theory has the following elements: (a) freedom consists in the power to act in accordance with one's choices, (b) freedom requires the ability to suspend desires and master passions, (c) freedom requires a power of self-motion in the agent, and (d) freedom is compatible with moral necessity but not with physical necessity. While these elements may at first appear disparate, the paper shows that they fit together quite well. The resulting theory is a surprising combination of doctrines that appear to be based on Samuel Clarke's libertarian account of free will and doctrines that are reminiscent of the compatibilist accounts of John Locke, Anthony Collins, Gottfried Leibniz, and Thomas Hobbes.