Morphological and phytogeographical data support the recognition of three distinct species in the genus Brachyelytrum: B. japonicum, B. erectum, and B. aristosum. Brachyelytrum japonicum is confined to eastern Asia and is characterized by narrow leaf blades (0.5–0.8 cm wide), long lower glumes (0.2–2.0 mm long), and long rachillas (6.8–8.8 mm long). Brachyelytrum erectum is distributed throughout much of the eastern United States, from northwestern Minnesota south to central Louisiana, east to northern Florida and north to northeastern New York. Brachyelytrum erectum is characterized by long hispid hairs (0.2–0.9 mm long) on the veins of the lemma, wide lemmas (0.8–1.8 mm wide), and a conspicuous lemma mid-vein. Brachyelytrum aristosum has a more northern distribution, occurring in southern Canada from southern Ontario to Newfoundland, the northern adjacent United States and through the Appalachian mountains to northwestern North Carolina. Brachyelytrum aristosum is characterized by short scaberulous hairs (0.06–0.2 mm long) on the lemma and narrow lemmas (0.7–1.4 mm wide) that are weakly veined. The distinctiveness of B. erectum and B. aristosum is further supported by amplified fragment length polymorphism (AFLP) data. We include a key to the taxa, synonymies, descriptions, and representative specimens. This study represents a recent monographic study of an eastern North American and eastern Asian disjunct genus.