Hanoi ( ha-NOY; Vietnamese: Hà Nội, pronounced [haː˨˩ noj˧˨ʔ] ) is the capital and second-most populous centrally-governed city of Vietnam. It covers an area of 3,358.6 km2 (1,296.8 mi2), and as of 2025 has a population of 8,807,523. Hanoi had the second-highest gross regional domestic product of all Vietnamese provinces and centrally-governed city at US$48 billion in 2023, behind Ho Chi Minh City. It hosts 78 foreign embassies, the headquarters of the Vietnam People's Army (VPA), its Vietnam National University system, and other governmental organizations. Hanoi had 18.7 million domestic and international visitors in 2022. It hosts the Imperial Citadel of Thăng Long, Ho Chi Minh Mausoleum, Hoàn Kiếm Lake, West Lake, and Ba Vì National Park near the outskirts of the municipality. Hanoi's urban area has architectural styles, including pre-colonial Vietnamese architecture, French colonial architecture, brutalist apartments and disorganized alleys and tube houses stemming from the city's growth in the 20th century.
In 1010, under the Lý dynasty, emperor Lý Thái Tổ established the capital of the imperial nation Đại Việt in what would later become central Hanoi, naming the city Thăng Long ([tʰɐŋ loŋ], 'ascending dragon'). In 1428, king Lê Lợi renamed the city to Đông Kinh ([ɗoŋ kīŋ̟], 'eastern capital'), with the city using this name until 1789. In 1802, the Nguyễn dynasty moved the national capital to Huế and the city was renamed Hanoi in 1831. Hanoi served as the capital of French Indochina from 1902 to 1945 and of the French protectorate of Tonkin from 1883 to 1949. After the August Revolution and the fall of the Nguyễn dynasty, the Democratic Republic of Vietnam (DRV) designated Hanoi as the capital of the newly independent country. From 1949 to 1954, Hanoi was part of the State of Vietnam. It was again part of the DRV from 1954 to 1976. In 1976, Hanoi became the capital of the unified Socialist Republic of Vietnam.
Contents
Names
Hanoi was known as Long Biên (龍編, lit. 'dragons interweaving'), then Tống Bình (宋平, lit. 'Song pacification') and Long Đỗ (龍肚, lit. 'dragon belly'). Long Biên later gave its name to the Long Biên Bridge, built during French colonial times. Some older names of Hanoi feature long (龍, transl. dragon), linked to the curved formation of the Red River around the city, which was symbolized as a dragon.
In 866, it was turned into a citadel and named Đại La (大羅, lit. 'big net'). This gave it the nickname La Thành (羅城, lit. 'La citadel'). When Lý Thái Tổ established the capital in the area in 1010, it was named Thăng Long (昇龍).
Arab manuscripts between the 9th and 12th century referred to Hanoi as Luqin (لوكين), a term derived from Longbian (Middle Chinese: Ljowng-pen), and was originally used by Muslim traders to mention the Vietnamese.
Environment
Hanoi sometimes ranks among the "most polluted cities", with days each year when it is the most air-polluted city in the world. According to the 2018 Global Air Quality Report, Hanoi's fine dust concentration was four times higher than the WHO's recommended limit (40.8 μg/m3 compared to the recommended 10 μg/m3). A report by Vietnam's Ministry of Natural Resources and Environment stated that Hanoi is the most air-polluted city in the country. The rivers flowing through Hanoi (Nhuệ River, Tô Lịch River, Kim Ngưu River, Lừ River, and Sét River) and some lakes are polluted, as 78% of Hanoi's wastewater is discharged directly into rivers and lakes without treatment. Each of these rivers receives tens of thousands of cubic meters of wastewater daily.
Climate
When using the Köppen climate classification, Hanoi is categorized as having a monsoon-influenced humid subtropical climate (Köppen Cwa) with precipitation like other places in Northern Vietnam. The city experiences the typical climate of Northern Vietnam, with four distinct seasons. Summer, from May to September, is characterized by hot and humid weather with more rainfall, and fewer dry days. Hot, dry conditions caused by westerly winds during summer are rarer. From October to November comprise the fall season, characterized by a decrease in temperature and precipitation, this time in the year mostly are warm and mild. Winters, from December to February, are characterized as being cool by the northeast monsoon, giving Hanoi a dry winter. Spring, from March until the end of April, Hanoi is characterized with some amounts of drizzle and less sunshine due to the activity of the southeast monsoon blowing moisture from the sea inland. and the Vietnam Institute for Building Science and Technology
The region has a positive water balance (i.e. the precipitation exceeds the potential evapotranspiration). Hanoi averages 1,612 millimetres (63.5 in) of rainfall per year, the majority falling from May to October. There are an average of 114 days with rain. The average annual temperature is 23.6 °C (74 °F), with a mean relative humidity of more than 80%. The coldest month has a mean temperature of 16.4 °C (61.5 °F) and the hottest month has a mean temperature of 29.2 °C (84.6 °F). The highest recorded temperature was 42.8 °C (109 °F) in May 1926, while the lowest recorded temperature was 2.7 °C (37 °F) on 12 January 1955. During a January 2016 cold wave, snow was seen to appear on the nearby Ba Vì mountain range, where the temperature fell to 0 °C (32 °F) on 24 January 2016.