The guenons (UK: /ɡəˈnɒnz/, US: /ˈɡwɛn.ənz/) are Old World monkeys of the genus Cercopithecus (/ˌsɜːrkəˈpɪθəkəs/). 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.^{[citation needed]}

All members of the genus are endemic to sub-Saharan Africa, and most are forest monkeys. Many of the species are quite local in their ranges, and some have even more local subspecies. Many are threatened or endangered because of habitat loss. The species currently placed in the genus Chlorocebus, such as vervet monkeys and green monkeys, were formerly considered as a single species in this genus, Cercopithecus aethiops.

In the English language, the word "guenon" is apparently of French origin.^[2] In French, guenon was the common name for all species and individuals, both males and females, from the genus Cercopithecus. In all other monkey and apes species, the French word guenon designates only the females.^[3] The three species such as the L'hoest's monkey, Preuss's monkey and the sun-tailed monkey were formerly included in the genus and now listed in a different genus Allochrocebus^[1][4][5]