Anarchy Online is a free-to-play sci fi MMORPG set 30,000 years in the future, on the desert world of Rubi-Ka. Players become a new colonist to Rubi-Ka, and must join one of three factions: Omni-Tek, The Clans, and a neutral faction. Since its launch in 2001, AO has built up a solid base of features, including having a level cap of 220, 4 humanoid breeds, 14 Professions, and 83 skills to choose from, along with being free to play.

Anarchy Online was the first sci fi MMORPG, and introduced instances to the genre. AO has a strong backstory, but remains sandbox by allowing players to choose how they play their characters, and for what reasons. Both solo and team play are well supported, as well as PvE, PvP, and roleplaying. A substantial game master group exists, called the Advisors of Rubi-Ka (ARK), who offer in game help to players, write and create (roleplaying) game events, and greet and assist new players.

AO has released 5 expansion since initial launch: Notum Wars (2002), Shadowlands (2003), Alien Invasion (2004), Lost Eden (2006), and Legacy of the Xan (2009). The graphics engine is currently undergoing an overhaul, changing from an older Dreamworld engine version to the newer version used in Age of Conan.