Defenders of the thesis of self-ownership generally focus on the “ownership” part of the thesis and say little about the metaphysics of the self that is said to be self-owned. But not all accounts of the self are consistent with robust self-ownership. Philosophical accounts of the self are typically enshrined in theories of personal identity, and the paper examines various such theories with a view to determining their suitability for grounding a metaphysics of the self consistent with self-ownership. As it happens, only one such theory is suitable: the hylemorphic theory of Aristotle and Aquinas. To adopt such a theory, however, is to see that self-ownership may in some respects have implications different from those many of its defenders take it to have.