Friedrich Nietzsche’s theory of eternal recurrence is an essential part of his mature philosophy, but the theory’s metaphysical commitments and practical implications are both obscure. In this essay I consider only the metaphysical elements of the theory, with the aim of determining whether it is possible that we live our lives infinitely many times, as the theory maintains. I argue that the possibility of eternal recurrence turns on issues in personal identity and the metaphysics of time. As I proceed, I also consider the relation between Nietzsche’s theory of eternal recurrence and theories of recurrence found in the work of Heraclitus, the Pythagoreans, and the Stoics.