Guild Wars is an episodic series of online 3D fantasy role-playing games developed by ArenaNet and published by NCsoft. Due to the fact that it deviated from traditional MMORPG norms in a number of areas, like instancing all the gameplay areas, and the fact that it focused more on PvP than most online RPGs, it was marketed as competitive online role-playing game. It provides two main modes of gameplay—a cooperative role-playing component and a competitive player vs. player (PvP) component—both of which are hosted on ArenaNet's servers. Three stand-alone episodes and one expansion pack were released in the series from April 2005 to August 2007.

The games depict the history of the fictional fantasy world of Tyria; each campaign focuses on events in disjoint sections of the world at roughly the same time. A player creates an avatar to play through the cooperative storyline of a campaign, taking on the role of a hero who must save Tyria from episode-specific antagonists. Players can group with other players and non-player characters, known as henchmen and heroes, to perform missions and quests found throughout the game-world. PvP combat is consensual, team based, and limited to areas designed for such combat. Players are allowed to create characters at maximum level and the best equipment specifically for PvP play, which is unusual for MMORPGs. ArenaNet hosts official Guild Wars tournaments where the most successful players and guilds may compete for the chance to play live at gaming conventions and win prizes up to US$100,000.