High Quality Content by WIKIPEDIA articles! The mandrill (Mandrillus sphinx) is a primate of the Old World monkey (Cercopithecidae) family, closely related to the baboons and even more closely to the drill. Both the mandrill and the drill were once classified as baboons in genus Papio, but recent research has determined they should be separated into their own genus, Mandrillus. The mandrill is the world`s largest species of monkey. Charles Darwin wrote, "no other member in the whole class of mammals is coloured in so extraordinary a manner as the adult male mandrills".