Released n/a
.hack//Outbreak (Japanese: .hack//侵食汚染 Vol.3 [Erosion Pollution – Vol.3]) is the third part in a series of four PlayStation 2 video games based within the .hack universe. The game simulates an MMORPG entitled The World and accomplishes this without requiring the player to ever actually venture online. The game is part of a serial storyline, with each of the four games slowly released over the course of a little over a year. .hack//Outbreak's storyline, preceded by .hack//Infection and .hack//Mutation, is followed by .hack//Quarantine.

Each installment of the game is accompanied by a DVD containing an episode of the .hack//Liminality OVA series. The four episodes happen in the real world, as opposed to the fictional MMORPG, The World, in which the game takes place entirely in. The events of Liminality take place alongside those of the games.

The games themselves feature a linear storyline that concludes in each installment with the player receiving a Data Flag. Once the Data Flag has been received, the file may be converted to the next game, allowing a player to start each additional chapter with any items and level ups they may have had on their original file. However, players may still start the game without having played any of the previous installments in the series.

At startup, players find themselves facing a mock desktop, complete with icons reading "The World", "Mailer", "News", "Accessory", "Audio", and "Data". The last allows the player to save their game data, while Accessory and Audio allow players to customize their desktop – changing the wallpaper, what background music is playing, or watch cinematics from the game. While these choices are all limited early on in the game, performing various tasks will allow players to unlock more of these special features. News opens up a browser, displaying various news information going on in the outside world that the game is set in. Mailer takes players to their e-mail inbox, where various characters they encounter through the course of the game will write to them – sometimes with simply humorous greetings and other times with tips and hints that steer the story towards its next plot point. It is the last icon, located at the top of the desktop, that sends the player off and running into the game.