The Tonkin snub-nosed monkey or Dollman's snub-nosed monkey, (Rhinopithecus avunculus), is a species of snub-nosed monkey endemic to northern Vietnam. Recorded at elevations between 200 to 1,200 m, its distribution is currently restricted to small fragmented tropical evergreen forests associated with steep karst limestone hills and mountains. Five isolated extant populations have been identified since its rediscovery in 1992. Despite heralded as a flagship species and subsequently receiving international attention and conservation actions, the population trend remains on the decline; therefore causing it to be continuously listed as one of "The World's 25 Most Endangered Primates." since the first global non-human primate biennial assessment began in 2001.