How Many Species of Monkeys Are There?

There are 329 living species of monkeys: 165 Old World monkeys and 164 New World monkeys. That count comes from version 2.4 of the Mammal Diversity Database, the American Society of Mammalogists' reference list, released in January 2026.

You will see much lower figures elsewhere — 260, 267, 270 are all common. Those are not wrong so much as out of date. The number of recognised monkey species has climbed steeply over the past two decades as genetic work has split populations that were previously treated as one, and reference works update at different speeds.

The two halves of the group

Monkeys divide into two branches that have been separate for roughly 35 million years.

Old World monkeys (family Cercopithecidae) live in Africa and Asia. This is the single largest primate family, with 165 living species in 23 genera. It splits almost evenly into two subfamilies: Cercopithecinae, the baboons, macaques, mangabeys and guenons, with 83 species; and Colobinae, the colobus monkeys, langurs and proboscis monkeys, with 82.

New World monkeys (parvorder Platyrrhini) live in Central and South America. There are 164 living species across five families and 20 genera.

| Family | Common names | Species | Genera | | --------------- | --------------------------------------------------------------- | ------- | ------ | | Cercopithecidae | Old World monkeys: baboons, macaques, guenons, colobus, langurs | 165 | 23 | | Pitheciidae | Titis, sakis, uakaris | 58 | 6 | | Callitrichidae | Marmosets and tamarins | 54 | 6 | | Atelidae | Howler, spider and woolly monkeys | 23 | 4 | | Cebidae | Capuchins and squirrel monkeys | 19 | 3 | | Aotidae | Night monkeys | 10 | 1 |

The two groups are easy to tell apart in practice. New World monkeys have sideways-facing nostrils and, in a few genera, prehensile tails that work as a fifth limb. Old World monkeys have downward-facing nostrils, no prehensile tails, and often sitting pads on the rump.

If you want to see how monkeys sit among the other 6,700-odd mammal species, our random mammal generator draws from the whole class.

Why sources disagree so much

Three things drive the spread between a count of 260 and a count of 330.

The first is simply the publication date. Many popular references still lean on Mammal Species of the World, whose third edition came out in 2005. Twenty years of sequencing has happened since.

The second is the species concept in use. Primatologists working on conservation have tended toward finer splitting, partly because a population recognised as a full species is easier to protect. Others prefer to keep such populations as subspecies. Neither approach is dishonest; they answer slightly different questions.

The third is that new monkeys are still being found. Titi monkeys, marmosets and tamarins in Amazonia have produced a steady run of descriptions, which is why Pitheciidae and Callitrichidae — the titis and the marmosets — are now the two largest New World families.

Are apes monkeys?

Traditionally, no. In everyday English and in most reference books, "monkey" means the 329 species above, and apes — gibbons, orangutans, gorillas, chimpanzees, bonobos and humans — are excluded.

That convention does not match the evolutionary tree. Apes emerged from within the Old World monkey lineage: the group Catarrhini contains the 165 Old World monkeys plus the 28 living apes, and the apes are nested inside, closer to some monkeys than those monkeys are to New World species. Cutting the apes out leaves what biologists call a paraphyletic group — a branch with a chunk removed.

So there are two consistent answers. Exclude apes, as almost everyone does, and you get 329 monkeys. Include them, because they sit inside the same branch, and you get 357 species of monkey, humans among them. The traditional answer is the useful one for most purposes; the cladistic answer is the one that matches the biology.

Monkeys as a share of all primates

The Mammal Diversity Database lists 509 living primate species. Monkeys make up 329 of those, or about 65 percent. The remainder are the 28 apes, plus lemurs, lorises, galagos and tarsiers — the primate lineages that are neither monkey nor ape.

Primates as a whole are a small slice of mammal diversity. Out of 6,758 living mammal species, primates account for well under a tenth. Rodents and bats between them make up more than half of all mammals.

Conservation

Monkey diversity is concentrated in tropical forest, which is also where habitat loss is fastest. A large share of the newly described Amazonian and Southeast Asian species are known from small ranges, and several are considered threatened from the moment they are named. Old World species are not uniformly at risk — macaques in particular have adapted well to human landscapes — but the langurs, colobus monkeys and lion-tailed macaques of Asia and Africa include some of the most endangered mammals anywhere.

The short version

329 living species, split almost exactly evenly between the Old World and the New. If a source tells you 260 or 270, it is probably working from a taxonomy fixed some time before 2010. Expect the figure to keep rising.

For a wider sample across the animal kingdom, try the random animal generator.