The Red River Delta or Hong River Delta (Vietnamese: Châu thổ sông Hồng) is the flat low-lying plain formed by the Red River and its distributaries merging with the Thái Bình River in northern Vietnam. Hồng (紅) is a Sino-Vietnamese word for "red" or "crimson". The delta has the smallest area but highest population and population density of all regions. The region, measuring some 15,000 square kilometres (6,000 sq mi) is well protected by a network of dikes. It is an agriculturally rich and densely populated area. Most of the land is devoted to rice cultivation.^[3]

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Quick Facts Châu thổ sông Hồng, Country ...

Red River Delta Châu thổ sông Hồng
Location of the Red River Delta region in Vietnam
Country	Vietnam
Area [1][2]
• Total	15,070.70 km2 (5,818.83 sq mi)
Population  (2022)[1]
• Total	22,091,250
• Density	1,500/km2 (3,800/sq mi)
GDP
• Metro	VND 1,753 trillion US$ 77.005 billion (2021)
Time zone	UTC+7 (UTC +7)

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Eight provinces, together with two municipalities (the capital Hanoi, and the port of Haiphong) form the delta. It had a population of almost 23 million in 2019.

In 2021, Paul Sidwell proposed that the locus of Proto-Austroasiatic languages was in this area about 4,000–4,500 years before present.^[4] The Hong River Delta is the cradle of the Vietnamese nation. Water puppetry originated in the rice paddies here. The region was bombed by United States warplanes during the Vietnam War. The region was designated as the Red River Delta Biosphere Reserve as part of UNESCO's Man and the Biosphere Programme in 2004.^[5]

• Quảng Ninh province, Bắc Giang province, Thái Nguyên province and Phú Thọ province are sometimes included as a province of the Red River Delta. Alternatively, they are seen as part of the Northeast region.
• Hà Tây province was merged into Hanoi in 2008.^[6]

Spanning some 150 km in width, the Red River Delta is located in the western coastal zone of the Gulf of Tonkin. The Red River is the second largest river in Vietnam and one of the five largest rivers on the East Asia coast. Its catchment covers parts of China and Vietnam and its water and sediment discharges greatly influence the hydrology in the Gulf of Tonkin.

In 2003, of the 78 million people in Vietnam, almost a third (24 million) live in the Red River basin, including over 17 million people in the delta itself. There are many large industrial zones in the Red River Delta clustering in Viet Tri, Hanoi, Haiphong and Nam Dinh. Most of the population works in rice cultivation but the delta region hosts other important economic activities such as fisheries, aquaculture, land reclamation for agriculture, harbor construction, mangrove forestry, etc. The socio-economic development in the delta is also affected by seasonal storms, flooding, coastal erosion, silting, salt water intrusion, etc.

Though the Red River Delta makes up only 5% of Vietnam's land, 30% of the country's population live there, making it the most densely populated part of the country. 80% of the population are employed in agriculture, but the agricultural lands of the delta amount to only about .3-.5 hectares per household, making the limited supply of arable lands a significant constraint to improving living standards.

Agriculturally the Red River Delta is the second most important rice-producing area in Vietnam, accounting for 20% of the national crop. Production of rice is close to optimal with very little yield gap to exploit and employing double cropping techniques to achieve close to maximum yields. However the rich soil of the delta does present a possibility of crop diversification and there is potential for further development of aquaculture.^[7] With these developmental pressures the estuarine environment and ecosystem face degradation due to threats of pollution, over-fishing and aquaculture destroying natural habitats..^[8]

• Red River Delta coalfield