Simon Says is a children's game for three or more players. One player takes the role of "Simon" and issues instructions (usually physical actions such as "jump in the air" or "stick out your tongue") to the other players, which should be followed only when prefaced with the phrase "Simon says". Players are eliminated from the game by either following instructions that are not immediately preceded by the phrase, or by failing to follow an instruction which does include the phrase "Simon says". It is the ability to distinguish between genuine and fake commands, rather than physical ability, that usually matters in the game; in most cases, the action just needs to be attempted.

The object for the player acting as Simon is to get all the other players out as quickly as possible; the winner of the game is usually the last player who has successfully followed all of the given commands. Occasionally, however, two or more of the last players may all be eliminated at the same time, thus resulting in Simon winning the game.

The game is embedded in popular culture, with numerous references in films, music, and literature.