A new species of woody bamboo (Poaceae: Bambusoideae), from Rio Doce State Park, Minas Gerais, Brazil, Merostachys tatianae is here described and illustrated. In its vegetative state the new species can be distinguished from all the known species in the genus by the longest internodes so far recorded for the genus (37–108 cm long) as well as by the huge culm-leaves (38–63.5 cm long). Both, the internodes and the culm-leaves are hispid, covered by irritating trichomes.