Red River (Vietnam)

Sông Hồng (红河)
Sông Thao, Hồng Hà, Nhị Hà, Nhĩ Hà, sông Cái, Nguyên Giang, Hóng Hé (pinyin)
Sông (河)
The Red River, view from Long Biên Bridge, Hanoi, Vietnam.
Countries	China, Vietnam
Provinces	Yunnan Province (China), Lào Cai Province, Yên Bái Province, Phú Thọ Province, Hanoi, Vĩnh Phúc Province, Hưng Yên Province, Hà Nam Province, Thái Bình Province, Nam Định Province
Tributaries
- left	Lô
- right	Đà
Source
- location	Hengduan Mountains, Weishan, Dali, Yunnan, China
- elevation	1,776 m (5,827 ft)
Secondary source
- location	TBD, Xiangyun, Dali, Yunnan, China
Source confluence
- elevation	1,200 m (3,937 ft)
- coordinates	25°1′49″N 100°48′56″E / 25.03028°N 100.81556°E / 25.03028; 100.81556
Mouth	Ba Lạt
- location	(boundary between Tiền Hải and Giao Thủy)
- elevation	0 m (0 ft)
- coordinates	20°14′43″N 106°35′20″E / 20.24528°N 106.58889°E / 20.24528; 106.58889Coordinates: 20°14′43″N 106°35′20″E / 20.24528°N 106.58889°E / 20.24528; 106.58889
Length	1,149 km (714 mi)
Basin	143,700 km2 (55,483 sq mi)
Discharge	mouth
- average	2,640 m3/s (93,231 cu ft/s)
- max	30,000 m3/s (1,059,440 cu ft/s)
- min	700 m3/s (24,720 cu ft/s)
Discharge elsewhere (average)
- Việt Trì	900 m3/s (31,783 cu ft/s)
Red River and its tributaries.

The Red River (simplified Chinese: 红河; traditional Chinese: 紅河; pinyin: Hóng Hé; Vietnamese: Sông Hồng), also known as the Hồng Hà and Sông Cái (lit. "Mother River") in Vietnamese and the Yuan River (, Yuán Jiāng) in Chinese, is a river that flows from Yunnan in Southwest China through northern Vietnam to the Gulf of Tonkin. According to C. Michael Hogan, the associated Red River Fault was instrumental in forming the entire South China Sea at least as early as 37 million years before present.

The Red River begins in China's Yunnan province in the mountains south of Dali. It flows generally southeastward, passing through Dai ethnic minority areas before leaving China through Yunnan's Honghe Autonomous Prefecture. It enters Vietnam at Lào Cai Province. It forms a portion of the international border between China and Vietnam. The river, known as Thao River for this upper stretch, continues its southeasterly course through northwestern Vietnam before emerging from the mountains to reach the midlands. Its main tributaries, the Black River (Da River) and Lô River join in to form the very broad Hồng near Việt Trì, Phu Tho Province. Downstream from Việt Trì, the river and its many distributaries spread out to form the Red River Delta. The Red River flows past the Vietnamese capital Hanoi before emptying into the Gulf of Tonkin.