Hanoi, also spelled Ha Noi, city, capital of Vietnam. The city is situated in northern Vietnam on the western bank of the Red River, about 85 miles (140 km) inland from the South China Sea. In addition to being the national capital, the capital of Vietnam, situated on the Red River in the north of the country; population 2,632,100 (est. 2009). It was the capital of French Indo-China from 1887 to 1946 and of North Vietnam before the reunification of North and South Vietnam.