Optimistic beliefs have been criticized by philosophers as being irrational or epistemically deficient. This paper argues for the possibility of a rational optimism. We propose a novel four-fold taxonomy of optimistic beliefs and argue that people may hold optimistic beliefs rationally for at least two of the four types (resourced optimism and agentive optimism). These forms of rational optimism are grounded in facts about one’s resources and agency and may be epistemically justified under certain conditions. We argue that the fourth (...) type of optimism in our taxonomy (perspectival optimism) is not subject to epistemic scrutiny in the same way. It is better evaluated on practical and moral grounds. This paper advances the discussion of optimism within both the philosophical and psychological literatures by providing a compelling and philosophically rich taxonomy of optimism that clarifies the sometimes-competing forms of optimism identified by psychologists. This advances the field by putting forward cases of epistemically justified optimism, in contrast with unrealistic optimism, that is sometimes justified for its instrumental or adaptive characteristics, and also by highlighting a form of optimism, perspectival optimism, that is not being considered in the mainstream optimism literature in psychology. The paper concludes by suggesting several avenues for future empirical and philosophical research. (shrink)