Allen's swamp monkey is a species of Old World monkey endemic to swamps and riparian forests in the central Congo Basin. As a medium-sized primate, adult individuals can have head-body lengths of up to 18 in (46 cm), with tails being slightly longer. It is identifiable by its coarse coat of green, brown, gray, and white fur. An arboreal omnivore, Allen's swamp monkey is typically found in trees adjacent to bodies of water, periodically descending to the ground to forage for a variety of invertebrates and plant matter in its riverine habitat. It is a diurnal, social animal that lives in groups of up to 40 individuals. Although it was once considered to be a guenon, Allen's swamp monkey has been taxonomized as the only member of the genus Allenopithecus since the 1920s, which is now regarded as a sister clade of the guenons. Despite being a cercopithecin, Allen's swamp monkey exhibits a pastiche of traits typical of papionins, as it has many primitive features of the Cercopithecinae subfamily. Allen's swamp monkey is classified as a least-concern species by the International Union for Conservation of Nature. Populations are projected to become threatened by poaching and live capture for the exotic pet trade.