Lang Son(redirected from Lang-son)
a city in the northern part of Vietnam (Bac Bo Province, Viet Bac Autonomous Region), on the Ky Cung River (basin of the Hsi River). Population, about 20,000. Lang Son is at the beginning of the trans-Indochina highway and railroad. It is also a center of the mining industry (bauxites, phosphates, and coal).