Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The Black River is a river located in China and northwestern Vietnam. Its source is in Yunnan Province of China. It runs through the provinces Lai Châu (where it forms part of the border with i n Biên Province), S n La and Hòa Bình. It is the most important tributary of the Red River, which it joins in Tam Nong District near Vi t Trì in Phú Th Province. It also forms part of the border between Phú Th Province and Hanoi (previously the border with Hà Tây Province). The rivers total length is 910 km, around 400 km in China and 527 km in Vietnam.