A new species of Phassus Walker, Phassus zapalinamensis sp. n., is described from northeastern Mexico based on a single male and female from the Parque Ecoturístico El Chorro (Coahuila) and the Área Natural Protegida Estatal "Cerro La Mota"(Nuevo León), with supplementary geographic records from photos posted at inaturalist.org. Conspecificity of the specimens is supported by a 100% bootstrap in the COI gene. Adults, male and female genitalia and external appearance are illustrated. The forewing pattern is most similar to P. huebneri (Geyer, [1838]), a species known only from illustration of the female moth which probably represents several cryptic species in Mexico and Central America. A syntype female specimen of Phassus marcius Druce, 1892 and a syntype female of Phassus argentiferus Walker, 1856 are designated here as respective lectotypes. The new species extends the previously documented range of Phassus between Central America and the trans-Mexican Volcanic belt, to almost the Mexico-United States border. This is currently the northernmost limit known for any genus of Hepialidae with Central or South American affinities. We discuss the potential evolutionary significance of the distributional boundary with respect to the possible role of the Jurassic-Cretaceous Mojave-Sonora Megashear fault system and earlier magmatic arcs in northern Mexico.