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