Mystacoleucus is a genus of barbs in the carp family, native to freshwater rivers and lakes across mainland and island Southeast Asia, from the Mekong basin through Myanmar and southern China down to Sumatra and Java. Members share the elongated, laterally compressed body typical of many regional cyprinids, along with a fine serrated spine at the front of the dorsal fin, a feature echoed in several unrelated "barb" genera and useful for telling the group apart at a glance. Atlas sizes span a wide range, from modest barb proportions up to a comparatively large 8 in.
The genus is better known regionally as a food fish than an aquarium one. Its most economically important member, the bilih (Mystacoleucus padangensis), is endemic to Lake Singkarak on Sumatra, where it has long supported an important local fishery; overfishing and hydroelectric development on the lake have driven serious declines, a pressure reflected in the genus's threatened species here. Most other Mystacoleucus rarely if ever appear in the aquarium trade, and detailed care information for the group is sparse.