Chu River (Nam Sam River)

Chu River (Vietnamese: Sông Chu), also known as the Nam Sam River or Nam Xam River (Laos), is the largest tributary of the Ma River. It begins at 2062m near Xam Neua town in Houaphanh Province in eastern Laos and travels east through Vietnam's Nghệ An and Thanh Hóa provinces. In Thiệu Hóa, it joins Ma River on the left. The Ma River is an Asian river that flows through northwestern Vietnam. It runs for 400 kilometers through Vietnam, Laos, and back through Vietnam before reaching the sea in the Gulf of Tonkin. The Chu River, along with the Bi River, and the Cầu Chày River all flow into the Ma River in Thanh Hóa Province, North Central Vietnam

The river is 325 kilometers long (165 kilometers in Laos and 160 kilometers in Vietnam), with a drainage area of approximately 7,580 kilometers (4,570 km2 in Laos and 3,010 km2 in Vietnam).

Length: 325 km (202 mi- shared with Laos)