Greyhawk is a fantasy campaign setting for the Dungeons & Dragons role playing game, originally developed as "the Great Kingdom" by Gary Gygax, ca. 1970, as a setting among his wargaming penpals. Gygax's medieval miniature game, Chainmail (1971) , on which he adapted the setting for his sessions, later morphed into Dungeons & Dragons role playing game (1974) when merged with Dave Arneson's more fantasy oriented setting Blackmoor. The World of Greyhawk boxed set published in 1980 was not the first campaign setting published by TSR Inc.; however it the setting most identified with early development of Dungeons & Dragons and Advanced Dungeons & Dragons.
Greyhawk was initially conceived by Gary Gygax as an underground dungeon oriented adventure for his group of friends which over time expanded to become a multi-layered underground complex near the city of Greyhawk, from which the campaign setting takes its name. Gary Gygax continued expanding the world to include the lands surrounding city of Greyhawk and finally the continent and the fictional world of Oerth in its entirety.
Integration into Dungeons & Dragons Online
Turbine did not officially license the Greyhawk intellectual property from / . A number of older modules that were set in the Greyhawk campaign setting have been licensed and brought to DDO in a generic unnamed world. With a large number of players familiar with the original pen and paper modules they are assumed to be Greyhawk.
As of September 2016 there are no public instances nor Wilderness Adventure Areas set in the unnamed world that players assumed to be Greyhawk Campaign Setting. All quests are accessed via dimension gate in the Halls of Heroes.