Annamese Cordillera (än'nämēz` kôr'dĭlyâr`ə), Fr. Chaîne Annamitique, principal mountain range of mainland Southeast Asia, extending c.700 mi (1,130 km) from N central Laos SE to S central Vietnam; Ngoc Linh (8,524 ft/2,598 m) in Vietnam is the highest peak. The range forms the divide between rivers draining into the Mekong basin and those flowing into the South China Sea. An igneous massif, the range has a steep eastern face and a gently sloping western section. The Tran Ninh Plateau in the north and the Moi plateaus in the south are extensions of the range.