A new euthyplociid burrowing mayfly (Polymitarcyidae, Ephemeroidea, Ephemeroptera), Polyplocia orientalis n. sp., from Vietnam is described with larval habitus and line drawings of mouthparts. The larva of the species is characterized by the mandibular tusks that bear numerous hairlike and stout setae on their dorsal and lateral surfaces and by the apical process of foretibiae that is nearly one-fourth the length of foretarsi. Its habitat and biological data and taxonomic remarks are provided. The burrowing mayfly subfamily Euthyplociinae is reviewed from a historical perspective.