The Preuss's monkey (Allochrocebus preussi), also known as Preuss's guenon, is a diurnal primate that lives terrestrially in mountainous (up to 2500 m) forests of eastern Nigeria, western Cameroon and Bioko in Equatorial Guinea. It was formerly classified as a subspecies of the L'Hoest's monkey (A. lhoesti).
Preuss's monkey is currently classified as a member of the genus Allochrocebus. It was formerly considered a member of the genus Cercopithecus.