Namtso or Lake Nam (officially: Nam Co; Mongolian: Tengri Nor; “Heavenly Lake”; (30°42′N90°33′E) is a mountain lake on the border between Damxung County of Lhasa prefecture-level city and Baingoin County of Nagqu Prefecture in the Tibet Autonomous Region of China, approximately 112 kilometres (70 mi) NNW of Lhasa.