Dungeons & Dragons Online is a massively multiplayer online role-playing game (MMORPG) developed by Turbine for Microsoft Windows and OS X. The game was originally marketed as Dungeons & Dragons Online: Stormreach. Upon switching to a hybrid free-to-play model it was renamed Dungeons & Dragons Online: Eberron Unlimited. The game was rebranded Dungeons & Dragons Online, with the introduction of Forgotten Realms-related content. Turbine developed Dungeons & Dragons Online as an online adaptation of Dungeons & Dragons (D&D), originally based loosely on the D&D 3.5 rule set. The game is set on the unexplored continent of Xen'drik within the Eberron campaign setting, and in the Kingdom of Cormyr within the Forgotten Realms campaign setting.

Eberron is a campaign setting for the Dungeons & Dragons (D&D) role-playing game. The game is set primarily on the continent of Khorvaire following a vast destructive war. Eberron is designed to accommodate traditional D&D elements and races within a differently toned setting; Eberron combines a fantasy tone with pulp and dark adventure elements, and some non-traditional fantasy technologies such as trains, skyships, and mechanical beings which are all powered by magic.