The Isle of the Ape consists of several tropical islands filled with dinosaurs, giant apes, and savage humans. The largest of the apes, Oonga, is king of the Isle of the Ape. The main island is 73 miles long in its longest dimension and features several smoking volcanoes that light the sky with a hellish glow.

An Olman tribe, originally from the Isle of Dread, also inhabits the Isle.

The Isle of the Ape was discovered in the 560s CY by Murlynd, Robilar, Tenser, and Terik, who found a portal to it beneath Castle Greyhawk. A decade later, Tenser lent a magical boat to an adventuring party including Agath of Thrunch, Reynard Yargrove, Franz, Lord Torkeep, Rowena of the Silverbrow, Warnes Starcoat, and Rakehell Chert. The magic boat transported them to the demiplane, where they recovered the Crook of Rao.