The genus Semia Matsumura that is from East Asia. According to Lee and Hill, 2010, this genus belongs to subtribe Psithyristriina within the tribe Cicadini. There are six species S. watanabei (Matsumura), S. klapperichi Jacobi, S. lachna Lei and Chou, S. majuscula Distant, S. spinosa Pham, Hayashi and Yang, and S. gialaiensis Pham and Constant. A revised description of the cicada species Semia watanabei (Matsumura, 1907) is provided. A key to the four Vietnamese Semia species: S. majuscula (Distant), S. watanabei (Matsumura), S. spinosa Pham, Hayashi and Yang, and S. gialaiensis Pham and Constant is provided. Synonymic lists and new locality records for the four species of Semia from Vietnam are provided.