Calamagrostis hongii, a new species ofCalamagrostis(Poaceae) from southwestern China (S Chongqing, W Guizhou, Sichuan, SE Xizang, Yunnan), is here described and illustrated. It is similar toC. arundinaceaandC. effusiflorain spikelet traits, but can be distinguished by its moderately or densely scabrous upper leaf surface with ribs covered by short, stiff, prickle hairs, and glabrous leaf sheaths, blades and collars. NomenclatureDeyeuxia zhongdianensislacks Latin description or diagnosis and is an unavailablenomen nudum(naked name).