Hope is among the most significant sources of motivation. It can also serve as a final barrier against despair. But among philosophers there is little agreement about what hope exactly is. Recent years have witnessed a steadily growing literature on the nature of hope, with nearly as many distinct theories as contributors. Furthermore, the question of how to define hope has downstream consequences for how we conceive of both the value of hope and its potential dangers. The entry closes with a brief discussion of the growing debate on whether hope can be a virtue.