Calamagrostis hongii, a new species of Calamagrostis (Poaceae) from southwestern China (S Chongqing, W Guizhou, Sichuan, SE Xizang, Yunnan), is here described and illustrated. It is similar to C. arundinacea and C. effusiflora in 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. Nomenclature Deyeuxia zhongdianensis lacks Latin description or diagnosis and is an unavailable nomen nudum (naked name).