Greyhawk, also known as the World of Greyhawk, is a campaign setting for the Dungeons & Dragons role-playing game (D&D). The World of Greyhawk includes the Free City of Greyhawk, from which the setting's name was taken. As one of the earliest D&D campaign settings, many of the rules for the game itself were developed in conjunction with game play by Gary Gygax and others in and around Castle Greyhawk and its dungeons.