諒山省
Mount Mẫu Sơn is a mountain in Lộc Bình District, Lạng Sơn Province, in northeastern Vietnam. It is located about 170 km northeast of the Hanoi and about 30 km east of Lạng Sơn City close to the international border between Vietnam and China. The highest peak of Mount Mẫu Sơn reaches about 1,600 m above sea level.