Castle Greyhawk is one of the central dungeon settings in the fictional World of Greyhawk campaign setting for the Dungeons & Dragons roleplaying game. The Castle was originally developed by Gary Gygax for his own campaign and later detailed for publication. Castle Greyhawk is also the name of a 1988 Dungeons & Dragons adventure module that offered a tongue-in-cheek treatment of the Castle. In 2005, Gary Gygax announced the release of "Castle Zagyg," his new treatment of the dungeon.