Lạng Sơn is a city in far Northern Vietnam, and the capital of Lạng Sơn Province. It is accessible by road and rail from Hanoi, the Vietnamese capital, and it is the northernmost point on National Route 1.

Lạng Sơn is a province in northern Vietnam. Its capital is also called Lạng Sơn, which is a strategically important town at the border with China and is 137 kilometres (85 mi) northeast of Hanoi connected by rail and road. Lạng Sơn province is bordered by Cao Bằng province, Bắc Giang province, Bắc Kạn province, Quảng Ninh province, Thái Nguyên province, and China's Guangxi province. The province covers an area of 8,310.18 km2 (3,208.58 sq mi) and as of 2008 it had a population of 781,655.