1A river in SE Asia, which rises in southern China and flows 1,175 km (730 miles) generally south-eastwards through northern Vietnam to the Gulf of Tonkin.
2A river in the southern US, a tributary of the Mississippi, which rises in northern Texas and flows 1,966 km (1,222 miles) generally south-eastwards, forming part of the border between Texas and Oklahoma, and enters the Mississippi in Louisiana. Also called Red River of the South.
3A river in the northern US and Canada, which rises in North Dakota and flows 877 km (545 miles) northwards, forming for most of its length the border between North Dakota and Minnesota, before entering Canada and emptying into Lake Winnipeg. Also called Red River of the North.