Dien Bien is a province in northwestern Vietnam. It is bordered by Lai Chau and Son La provinces of Vietnam to the east and south, Pu'er City, Yunnan, China, to the north, and Phongsaly Province in Laos to the west. Dien Bien is a new province which was created by dividing the former Lai Chau Province in early 2004, both themselves were once part of the Lan Xang kingdom, then switched ownership to Vietnam during the French Colonial period. Dien Bien includes all the land to the south of the Da River (Black River), and New Lai Chau Province includes all the land to the north of the Da River.