The Dying Earth is the setting of fantasy novels (Eyes of the Overworld, Cugel's Saga, Rhialto the Marvellous) and short stories (collected as The Dying Earth) by the great Jack Vance. These had considerable influence on Gary Gygax in writing D&D, particularly on the magic system. Nevertheless, as fantasy RPG settings have wandered ever more deeply into the post-Tolkienian pseudo-mediaeval, the Dying Earth has been left as a non-conventional fantasy setting.
Dying Earth RPG
The Dying Earth is also a licensed fantasy RPG set in Vance's setting, with mechanics designed to support the picaresque tone of the original works.