Ichnanthus belongs to the grass subfamily Panicoideae and is characterized by the presence of winged appendages at the base of the upper lemma or by their scars. The genus includes about 30 species that predominate in Neotropical forests, with a great diversity found in Brazil. A new species, Ichnanthus longhi-wagnerii, is herein described, illustrated, and compared with its congeners. We also present geographical and ecological information, as well as SEM micrographs of the upper anthecium. This new species was previously collected in a submontane Atlantic moist forest in Southern Bahia, Brazil, but was not found during recent fieldtrips and is therefore considered endangered.