Alnus betulifolia G.Y. Li, Z.H. Chen & D.D. Ma (Betulaceae), a new species of Betulaceae from Zhejiang, eastern China, is described and illustrated. It is similar to the Japanese endemic A. firma, but differs from it by being a shrub, often 2–3 m tall, and by having male inflorescences single and compact, and female inflorescences usually single or double in lateral branches above male inflorescences.