Every day, people tell each other, “Have fun!” Psychologists often regard fun as a motive for behaviors or beliefs. A few organizational psychologists have provided more theoretical accounts of fun, typically in order to explore the effects of fun on employee motivation and job performance or in order to “make learning fun.” Surprisingly, there is no extant philosophical account of fun. I develop a philosophical typology of fun, adventure, play, and pleasure. Fun is distinct from pleasure because it necessarily involves some degree of uncertainty about what will happen next and because it involves not taking what one is doing too seriously. My account allows us to distinguish between fun and pseudo-fun, providing a foundation for a critique of merely manipulative attempts to make work and school “fun.”