De Brazza's monkey (Cercopithecus neglectus) is an Old World monkey endemic to the riverine and swamp forests of central Africa. The largest species in the guenon family, it is one of the most widespread arboreal African primates. Aside from size, it can be differentiated from other cercopithecus monkeys by its orange diadem and white beard. Due to its cryptic nature, the species is not well documented in all of its habitats but has shown unique traits such as pair-bonding and aggressive behavior towards other guenons.

De Brazza's monkeys range across the swamps, bamboo and dry mountain forests of Angola, Cameroon, Central African Republic, Congo, The Democratic Republic of the Congo, Equatorial Guinea, Ethiopia, Gabon, Kenya, South Sudan, Nigeria and Uganda and possibly Tanzania though reports have not been confirmed. Troops are found almost exclusively near water, rarely venturing farther than 1 km away from a river or tributary. As a result they can sometimes be seen swimming. The monkeys prefer dense forest and vegetation, only venturing into more open forest to feed. They are mainly arboreal, but descends to the ground to feed on herbaceous plants. Due to its cryptic nature there is no accurate population estimate for the species over its entire range.