Pokémon Colosseum is a role-playing video game developed by Genius Sonority and published by The Pokémon Company and Nintendo for the GameCube. A spin-off of the Pokémon series, it was released on November 21, 2003, in Japan, March 22, 2004, in North America and May 14, 2004, in Europe.

Unlike previous titles' random encounters with Pokémon, Colosseum allows the player to steal ("snag") the Pokémon of other Pokémon Trainers. The game also features single-player and multiplayer battle modes.

Pokémon Colosseum is a 3D role-playing game viewed from a third-person perspective. The player, controlling a Pokémon Trainer named Wes (default name), moves through various towns and other locations (traversed using a type of one-wheeled motorcycle), battling enemy Trainers and completing quests.

When a battle starts, the screen switches to a turn-based interface where the player's and enemies' Pokémon fight. Most battles are of the "double battle" format, which means two Pokémon on each side at one time. However, each Trainer can carry up to six Pokémon at one time, so once a Pokémon is defeated, his or her Trainer must switch out another one unless no more are left. Battles are also conducted at "Colosseums" in several cities.

Unlike most Pokémon games, Colosseum does not feature random encounters. The player begins the game with two Pokémon. More are obtained throughout the game by "Snagging" them from other Trainers using Poké Balls of various strengths. Only specifically designated "Shadow Pokémon", whose hearts have been artificially closed, can be Snagged. This contrasts with the normal means of acquiring Pokémon by catching them from the wild in other games. Pokémon can be traded between Colosseum and the Game Boy Advance games Ruby, Sapphire, FireRed, LeafGreen and Emerald.