.hack//G.U. is a series of single-player action role-playing games for the PlayStation 2, developed by CyberConnect2 and published by Bandai Namco Entertainment between 2006 and 2007. The series contains three games: .hack//G.U. Vol. 1//Rebirth, .hack//G.U. Vol. 2//Reminisce and .hack//G.U. Vol. 3//Redemption. As in the previous .hack games, .hack//G.U. simulates a massively multiplayer online role-playing game (MMORPG) called The World—the player controls a character who plays the fictional online game. They were directed by Hiroshi Matsuyama who aimed to address criticisms of the previous series. Its narrative, by Tatsuya Hamazaki, was written concurrently with .hack//Roots, an anime set before the events of the games.

.hack is a series of single-player action role-playing video games developed for the PlayStation 2 console by CyberConnect2 and published by Bandai. The four games, .hack//Infection, .hack//Mutation, .hack//Outbreak, and .hack//Quarantine, all feature a "game within a game", a fictional massively multiplayer online role-playing game (MMORPG) called The World which does not require the player to connect to the Internet. Players may transfer their characters and data between games in the series. Each game comes with an extra DVD containing an episode of .hack//Liminality, the accompanying original video animation (OVA) series which details fictional events that occur concurrently with the games.