The female and male of Simulium (Montisimulium) angkaense are described for the first time, based on adult specimens reared from pupae and/or larvae collected from the Siribhume waterfall (type locality), Chiang Mai, Thailand. The female and male of this species are compared with those of S. (M.) merga and the female of S. (M.) surachaii, both of which were recorded from Thailand.
