There has been a long tradition of interpreting Plato as a rational egoist. Over the past few decades, however, some scholars have challenged this reading. While Rational Egoism appeals to many ordinary folk, in sophisticated philosophical circles it has fallen out of favor as a general and complete account of the nature of reasons for action. I argue that while the theory of practical rationality that is often equated with rational egoism—a view that I call ‘Simple-Minded Rational Egoism'—is neither plausible nor endorsed by Plato in his Republic, there is a more complex version of Rational Egoism to which Plato is indeed committed. Moreover, such a conception of practical rationality is not vulnerable to the standard set of objections that contemporary philosophers have made against Rational Egoism.