In psychology and ethology, play is a range of voluntary, intrinsically motivated activities normally associated with recreational pleasure and enjoyment. Play is most commonly associated with children and their juvenile-level activities, but play can also be a useful adult activity, and occurs among other higher-functioning animals as well.

Many of the most prominent researchers in the field of psychology (including Jean Piaget, William James, Sigmund Freud, Carl Jung and Lev Vygotsky) have viewed play as endemic to the human species. These psychologists all had strong beliefs on how important play was on human development. Many research methods were performed to prove their theories.

Play is often interpreted as frivolous; yet the player can be intently focused on his or her objective, particularly when play is structured and goal-oriented, as in a game. Accordingly, play can range from relaxed, free-spirited and spontaneous through frivolous to planned or even compulsive.