The world's rarest monkeys are not defined by a single official ranking. Conservation status, population size, geographic range, and the quality of available surveys all matter. Some species survive in only a few forest fragments or a handful of protected areas, while others remain slightly more numerous but are declining rapidly.
This updated list focuses only on true monkeys. The previous version mixed monkeys with lemurs, lorises, and galagos, which are primates but are not monkeys. It also relied on several outdated population estimates. The species below are among the rarest and most threatened monkeys currently known, with many classified as Critically Endangered.
10 of the Rarest Monkeys in the World
| Monkey | Scientific name | Region | Global status | Main threats |
|---|---|---|---|---|
| Roloway monkey | Cercopithecus roloway | Ghana and Côte d'Ivoire | Critically Endangered | Hunting and forest loss |
| Niger Delta red colobus | Piliocolobus epieni | Nigeria | Critically Endangered | Hunting and habitat destruction |
| Tana River red colobus | Piliocolobus rufomitratus | Kenya | Critically Endangered | Forest fragmentation and habitat loss |
| Cat Ba langur | Trachypithecus poliocephalus | Cat Ba Island, Vietnam | Critically Endangered | Small population, habitat pressure, past hunting |
| Delacour's langur | Trachypithecus delacouri | Northern Vietnam | Critically Endangered | Quarrying, hunting, forest loss |
| Tonkin snub-nosed monkey | Rhinopithecus avunculus | Northern Vietnam | Critically Endangered | Hunting and forest degradation |
| Myanmar snub-nosed monkey | Rhinopithecus strykeri | Myanmar and China | Critically Endangered | Hunting and habitat fragmentation |
| Brown-headed spider monkey | Ateles fusciceps | Colombia and Ecuador | Critically Endangered | Deforestation and hunting |
| Golden langur | Trachypithecus geei | India and Bhutan | Endangered | Fragmentation, roads, power lines, habitat loss |
| Guizhou snub-nosed monkey | Rhinopithecus brelichi | Guizhou, China | Critically Endangered | Very restricted range and habitat pressure |
The Roloway monkey is a Critically Endangered West African monkey threatened by hunting and forest loss.
What Does “Rarest Monkey” Actually Mean?
There is no scientific organization that publishes a permanent first-to-tenth ranking of the world's rarest monkeys. A species can be considered exceptionally rare because its total population is tiny, because it survives in only a very small geographic area, or because only a few isolated populations remain.
Conservation categories are also not the same thing as a rarity ranking. The IUCN Red List uses categories such as Vulnerable, Endangered, and Critically Endangered to measure extinction risk. A Critically Endangered species is facing an extremely high risk of extinction in the wild, but two Critically Endangered species may still differ greatly in population size and distribution.
For that reason, the list below should be read as 10 of the rarest monkeys, not as a scientifically fixed ranking from rarest to least rare.
Roloway Monkey
The Roloway monkey (Cercopithecus roloway) is one of West Africa's most threatened monkeys. It is restricted to forests in Ghana and Côte d'Ivoire and is classified as Critically Endangered.
The species has disappeared from much of its former range. Hunting for bushmeat and extensive forest loss are the main pressures. The Roloway monkey has repeatedly appeared in international lists of the world's most endangered primates.
Its black-and-white face, dark body, and contrasting white chest make it easy to distinguish from many related guenons, but seeing one in the wild has become increasingly difficult.
Niger Delta Red Colobus
The Niger Delta red colobus (Piliocolobus epieni) is endemic to the western Niger Delta in Nigeria. It is classified as Critically Endangered and survives in a highly fragmented landscape.
The species was only recognized by science in the 1990s and was later treated as a full species. Hunting and the destruction of swamp and lowland forest are the dominant threats.
Tana River Red Colobus
The Tana River red colobus (Piliocolobus rufomitratus) is found in a narrow belt of riverine forest along Kenya's lower Tana River. Its dependence on scattered forest patches makes the species especially vulnerable to habitat fragmentation.
Loss of riverine forest for farming, settlement, timber use, and other land changes has reduced and isolated its habitat. The species is classified as Critically Endangered.
Like other red colobus monkeys, it is mainly arboreal and depends heavily on connected forest canopy for feeding and movement.
Cat Ba Langur
The Cat Ba langur (Trachypithecus poliocephalus), also called the golden-headed langur, is endemic to Cat Ba Island in northern Vietnam. It is one of the rarest monkeys in Asia and is classified as Critically Endangered.
The species survives in limestone karst habitat, where steep cliffs and isolated forest patches limit both movement and available habitat. Conservation programs have helped protect the remaining groups, but the total population is still extremely small.
The Cat Ba langur should not be confused with the golden langur (Trachypithecus geei) of India and Bhutan. They are different species.
Delacour's Langur
Delacour's langur (Trachypithecus delacouri) is another Critically Endangered Vietnamese monkey specialized for limestone landscapes. Fauna & Flora estimates that only about 250 remain in the wild, concentrated in a very small number of viable populations.
Its black-and-white coat is distinctive, but its habitat is disappearing. Limestone quarrying for cement, forest degradation, and past hunting have placed intense pressure on the species.
Conservation work in northern Vietnam has focused on protecting the remaining karst forests and expanding protection around important populations.
Tonkin Snub-Nosed Monkey
The Tonkin snub-nosed monkey (Rhinopithecus avunculus) is endemic to northern Vietnam and is classified as Critically Endangered. It was once feared extinct before being rediscovered in the late twentieth century.
Today, the species is known from only a few areas. Fauna & Flora reports that the largest surviving population, at Khau Ca, has grown to around 160 individuals following years of protection. Other populations remain much more precarious.
A 2024 survey in Quan Ba forest failed to find direct evidence of the species there, highlighting how fragile some of the remaining populations have become.
Myanmar Snub-Nosed Monkey
The Myanmar snub-nosed monkey (Rhinopithecus strykeri) was scientifically described only in the early 2010s. It occurs in mountainous forests of northern Myanmar and adjacent China.
The species is Critically Endangered. Earlier surveys estimated fewer than 1,000 animals across its known range, although exact totals remain uncertain because the terrain is remote and difficult to survey.
Hunting and habitat fragmentation are major threats. Its upturned nose is extremely distinctive and inspired reports that rain entering the nostrils can make the monkeys sneeze.
Brown-Headed Spider Monkey
The brown-headed spider monkey (Ateles fusciceps) is a Critically Endangered New World monkey found in northwestern South America. It depends on mature tropical forest and travels through the canopy using long limbs and a powerful prehensile tail.
Deforestation has reduced and fragmented its habitat, while hunting adds further pressure. Spider monkeys also reproduce slowly, which means populations recover poorly after adult numbers are reduced.
Golden Langur
The golden langur (Trachypithecus geei) is an Endangered leaf-eating monkey found in a restricted region of Assam in India and neighboring Bhutan. Its pale golden or cream-colored coat and dark face make it one of the most recognizable Asian langurs.
The previous version of this article incorrectly called it the “golden-headed black leaf monkey,” which can be confused with the Cat Ba langur. The accepted common name for Trachypithecus geei is golden langur.
Habitat fragmentation is a major concern. Roads, settlements, forest clearing, and power infrastructure can divide groups and increase mortality when monkeys attempt to cross between forest patches.
Guizhou Snub-Nosed Monkey
The Guizhou snub-nosed monkey (Rhinopithecus brelichi), also called the gray snub-nosed monkey, has one of the most restricted ranges of any monkey. It is found only around Fanjingshan in Guizhou Province, China.
Modern conservation references classify the species as Critically Endangered. Its limited distribution means that habitat degradation, disturbance, and other local threats can affect a large proportion of the global population at once.
Why the Previous List Needed Updating
The older version of this article mixed several different primate groups together. Northern sportive lemurs, Javan slow lorises, and Rondo dwarf galagos are all primates, but they are not monkeys.
That distinction matters. Primates include:
monkeys
apes
lemurs
lorises
galagos
tarsiers
All monkeys are primates, but not all primates are monkeys. This revised article therefore limits the Top 10 list to true monkeys.
What Is Driving Rare Monkeys Toward Extinction?
The exact pressures differ by country and species, but the same threats appear repeatedly:
Deforestation: clearing forest for agriculture, settlement, roads, logging, and infrastructure.
Fragmentation: dividing one forest into small isolated patches that cannot support healthy populations.
Hunting: killing primates for bushmeat, traditional uses, or local trade.
Wildlife trafficking: capture of live young animals and illegal trade in body parts.
Mining and quarrying: especially serious for species restricted to limestone karst habitats.
Small population size: tiny populations are more vulnerable to disease, inbreeding, natural disasters, and random population changes.
Are the Rarest Monkeys Always the Most Endangered?
Usually there is substantial overlap, but “rare” and “endangered” are not identical terms. A naturally rare species may have always existed at low density but remain relatively stable, while a formerly common species can become Endangered after a rapid decline.
The IUCN Red List evaluates extinction risk using multiple criteria, including population decline, population size, geographic range, and fragmentation. That approach is more informative than simply counting how many animals are believed to remain.
Frequently Asked Questions
What is the rarest monkey in the world?
There is no permanent scientific ranking naming one single “rarest monkey.” Species such as the Cat Ba langur, Delacour's langur, Roloway monkey, Tonkin snub-nosed monkey, and several red colobus monkeys are among the rarest because they survive in very small or fragmented populations.
Is the Cat Ba langur a monkey?
Yes. The Cat Ba langur is an Old World monkey in the family Cercopithecidae. It is endemic to Cat Ba Island in Vietnam.
Is a slow loris a monkey?
No. Slow lorises are primates, but they are not monkeys. They belong to a different primate lineage.
Are lemurs monkeys?
No. Lemurs are primates native to Madagascar, but they are not monkeys. This is why northern sportive lemurs were removed from the revised Top 10 list.
Why are so many rare monkeys found in Vietnam?
Vietnam has high primate diversity and many species with naturally restricted ranges. At the same time, hunting, forest fragmentation, and limestone quarrying have severely affected several endemic or near-endemic monkeys.
Which rare monkey has the smallest range?
Several species have extremely restricted ranges. The Cat Ba langur is limited to Cat Ba Island, while the Guizhou snub-nosed monkey is restricted to the Fanjingshan region of China.
Can rare monkey populations recover?
Yes, if threats are reduced. Protected habitat, anti-poaching work, community conservation, habitat restoration, and long-term monitoring can stabilize or increase populations. The Tonkin snub-nosed monkey population at Khau Ca is one encouraging example.
Official and Reference Sources
Final Takeaway
The world's rarest monkeys are concentrated in a few remaining forests, islands, river systems, and mountain habitats. Roloway monkeys, red colobus monkeys, Cat Ba and Delacour's langurs, snub-nosed monkeys, and brown-headed spider monkeys all face serious extinction risk. The most important correction to the older version of this page is simple: rarity should be based on current conservation evidence, and lemurs, lorises, and galagos should not be labeled as monkeys.
