Hide-and-seek (sometimes known as hide-and-go-seek) is a popular children's game in which at least two to three players conceal themselves in a set environment, to be found by one or more seekers. The game is played by one chosen player (designated as being "it") counting to a predetermined number with eyes closed while the other players hide. After reaching this number, the player who is "it" calls "Ready or not, here I come!" or "Coming, ready or not!" and then attempts to locate all concealed players.

The game can end in one of several ways. The most common way of ending is the player chosen as "it" locates all players; the player found first is the loser and is chosen to be "it" in the next game. The player found last is the winner. Another common variation has the seeker counting at "home base"; the hiders can either remain hidden or they can come out of hiding to race to home base; once they touch it, they are "safe" and cannot be tagged.

The game is an example of an oral tradition, as it is commonly passed by children.