In general, these monkeys are arboreal forest dwellers. The basic social unit is the family, consisting of one male and two or three females and young. The families are territorial, and the males utter loud barks or chirps as spacing calls, but families of different species will often combine for foraging, at times associating for long periods. Guenons forage for leaves, fruit, and other vegetation and possibly for insects and other small animals; several species raid crops. Breeding seems to occur at any time of year; single young are born after a gestation period of approximately five to seven months, depending on the species. Numerous species can be tamed, and they are commonly seen in zoos owing to their hardiness, activity, good nature, and habit of grimacing at observers. With good care, their life span may exceed 20–30 years.

Guenons are primates (primate) of the family Cercopithecidae (Old World monkeys). Chlorocebus species include the grivet (C. aethiops) of northeastern Africa, the vervet (C. pygerythrus) of eastern and southern Africa, and the green monkey (C. sabaeus) of West Africa. These largely ground-dwelling guenons are sometimes known collectively as savanna monkeys because they are found in open country or in woodland, as opposed to rainforest. They are greenish with pale yellow or white underparts and black faces. The grivet has a white tuft on the tip of the tail and a thin white browband that continues into backswept white whiskers. The vervet has shorter whiskers and black hands, feet, and tail tip. The green monkey has yellow whiskers, grayish hands and feet, and a yellow and black tail. Savanna monkeys live in larger social groups than other guenons, consisting of several males and 10 or more females and their young.

Species of the genus Cercopithecus have patches of short contrasting fur on the nose. The large spot-nosed guenon, or putty-nosed monkey (C. nictitans), is a common West African form with gray-flecked black fur and an oval yellowish or white nose spot. Among other species with nose patches are the lesser spot-nosed guenon (C. petaurista) and the redtail (C. ascanius), both with heart-shaped white nose spots.

Some guenons are generally known by other names, among them the diana monkey (including the roloway), the owl-faced monkey (also called Hamlyn's monkey), the mona monkey, and DeBrazza's monkey. Other guenons include the patas monkey (genus Erythrocebus), the talapoin, or mangrove monkey (genus Miopithecus), and the robust Allen's swamp monkey (genus Allenopithecus).