Probarbus is a genus of large migratory barbs in the carp family Cyprinidae, native to the Mekong and other major river systems of mainland Southeast Asia, with atlas records from Cambodia, Laos, Thailand, Vietnam, Malaysia and Myanmar. The atlas covers 3 species, and these are genuinely big cyprinids, recorded up to around 59 in, among the largest members of their family anywhere in the world. Probarbus species undertake long-distance spawning migrations along major rivers, a life history that ties their survival directly to the free flow of the rivers they inhabit.
Probarbus jullieni, the Isok barb, is the best known of the three and has long been a prized food and game fish in the region, as well as a species of cultural significance in Thailand. Probarbus labeamajor (thicklip barb) and Probarbus labeaminor (thinlip barb) were later recognised as distinct from the jullieni complex. All three now face serious conservation concern, and the genus is a stark case study in migratory-fish decline: the IUCN tally includes a Critically Endangered and an Endangered listing alongside one species not yet evaluated, driven mainly by dam construction blocking migration routes, overfishing and river habitat loss. None carry a CARES designation in the atlas at present, and the genus has essentially no presence in the aquarium hobby given both its size and conservation status.