Begonia xishuangbannaensis W.G. Wang & L.J. Jiang (Begoniaceae), a new tuberous species from Yunnan, China, is described and illustrated. It belongs to Begonia sect. Diploclinium. Morphologically, it is similar to B. fimbristipula and B. exposita in its tuberous habit and pubescent leaves, but can be distinguished from both by its asymmetrical leaf blade, 16-18 stamens, filaments that are free at base, and pistillate flowers having five tepals.