Two gallotannins (I and II) and an ellagitannin (III) named nupharin A have been isolated from Nuphar japonicum DC. (Nymphaeaceae). On the basis of chemical and spectral evidence, the structures of I, II and III were characterized as 1, 2, 6-tri-O-galloyl-α-D-glucose, 1, 2, 3, 4, 6-penta-O-galloyl-α-D-glucose and 1, 2, 6-tri-O-galloyl-3, 4-(S)-hexahydroxydiphenoyl-α-D-glucose, respectively.