Hamadryas, also called sacred baboon, or Arabian baboon, a large, powerful monkey of the plains and open-rock areas of the Red Sea coast, both in Africa (Eritrea, The Sudan) and on the opposite coast in Yemen and Saudi Arabia. The hamadryas is the smallest baboon species, with a body length of about 60–70 cm (24–28 inches) and weight of up to 18 kg (40 pounds). Females are brown, but males are silvery gray with an enormous cape of hair on the neck and shoulders.

Hamadryas baboons are large-bodied monkeys with a strong build and a dog-like muzzle. Both males and females have brown or light gray fur. While the females have hairless black and brown faces, the male hamadryas baboon has a distinctive mantle (mane) of long silvery hair and a bright pink face and backside. These baboons sport a relatively short, tufted tail that is not prehensile.