A new species and a new series of Elatostema (Urticaceae) from south-western China.

The new series ElatostemasectionWeddellia series Xingyiensia L.D. Duan & D.H. Yin (Urticaceae) is described. In addition, its new species Elatostemaxingyiense L.D. Duan & D.H. Yin, endemic to Guizhou Province, is also described and illustrated with photographs. The new series is morphologically similar to series Melanocarpa W.T. Wang and series Sublinearia W.T. Wang. The new species is most similar to E.melanocarpum, E.sublineare, E.obscurinerve, E.langicuspe and E.youyangense in morphology, but can be visibly distinguished by a combination of characters, including leaf vein, male inflorescences, female inflorescences and persistent tepals.