Guild Wars is an episodic series of multiplayer online role-playing games created by ArenaNet, a Seattle game development studio and a subsidiary of the South Korean game publisher NCsoft. Three stand-alone episodes and one expansion pack were released in the series from April 2005 to August 2007. All Guild Wars games run on the Microsoft Windows platform.

Guild Wars provides two main modes of gameplay¡ªa cooperative role-playing component and a competitive player vs. player (PvP) component¡ªboth of which are hosted on ArenaNet's servers. The games depict the history of the fictional fantasy world of Tyria, each campaign focusing on events in disjoint sections of the world, but roughly parallel in 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 or 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 100,000 USD.

The games in the Guild Wars series were critically well received and won many editor's choice awards, as well as awards such as best value, best massively multiplayer online role-playing game (MMORPG), and best game. Guild Wars was noted for being one of the few commercially developed games in the MMORPG genre to offer online play without subscription fees, its instanced approach to MMORPG play, and the quality of the graphics and play for computers with low specifications. In February 2008, NCSoft announced that 5 million units of games in the Guild Wars series had been sold. The sequel, Guild Wars 2, was announced in March 2007. It will have updated graphics and gameplay mechanics, and will continue the original Guild Wars tradition of no subscription fees. No release date has been announced.