The Diana monkey is an Old World monkey found in the high canopy forests in Sierra Leone, Liberia, and western Côte d’Ivoire Named for its white brow which is said to resemble the bow of the Roman goddess Diana, this black-grey guenon has a white throat, crescent-shaped browband, ruff and beard.

The guenons are Old World monkeys of the genus Cercopithecus. Not all members of this genus have the word "guenon" in their common names; also, because of changes in scientific classification, some monkeys in other genera may have common names that include the word "guenon". Nonetheless, the use of the term guenon for monkeys of this genus is widely accepted.