Orthetrum triangulare is an Asian freshwater dragonfly species. The common name for this species is blue-tailed forest hawk. Two subspecies of Orthetrum triangulare are currently recognised, the nominate subspecies and O. t. malaccense.

Description and habitat: It is a medium-sized dragonfly with dark face and bluish eyes. Its thorax is also black with a broad apple green stripe on both sides. Segments 1-2 and 8–10 in the abdomen are black and the remaining segments are pruinosed with azure blue. It is usually found in marshes associated with hill streams where it breeds.