Gorilla is a genus of the family Hominidae, a classification of lifeform that includes many species of gorillas, chimpanzees, orangutans, and humanoids. All these species characteristically walk on two legs, have a large brain-to-body mass ratio, and rely on vision as their primary sense.
There are at least two species of gorilla native to Earth (Gorilla gorilla and Gorilla beringei). Sentient, highly-intelligent gorillas exist on the planets Angoma, Tekton, and Zeltok, as well as on at least one alternate Earth.
Early in the first five-year mission, c. 2266, Captain Kirk sat down to a diplomatic dinner with KingKut, leader of the ancient gorilla people of Angoma. These gorillas were a warrior race in their declining years, who sought peaceful alliances as a defense against warlike species on nearby planets, including the Mantis, who were surreptitiously transporting groups of gorillas offworld. Later, in a sports arena, one gorilla played a game of soccer against a team from the Enterprise, winning by himself 16-2. (TOScomic: "Beware the Beast")