Breynia enchengensis, a new species with a narrowly geographic distribution in limestone areas of southwestern Guangxi, China, is described and illustrated. The new species is morphologically similar to B. poomae (Welzen & Chayam.) Welzen & Pruesapan in having creeping stems, ovate to oblong leaf blade and reddish brown to dark purple flowers, but can be easily distinguished from the latter by the size of leaf blade and flowers, the number of lateral veins, the growing way of inflorescence and the shape of ovary. A table to distinguish the new species from B. poomae, as well as color plates and type specimens of the new species are also provided.