Great apes are creatures believed to have resided on Earth by the inhabitants of the Koprulu Sector. Known for climbing buildings and swatting down primitive aircraft, they are believed to be one and the same species as gorillas.
Trivia
In all likelihood, the great apes have arisen from a misinterpretation of the data of ATLAS, taking the movie King Kong a bit too literally.
References
Grubb, Jeff (February 27, 2001). StarCraft: Liberty's Crusade. Simon & Schuster (Pocket Star). ISBN 0-671-04148-7