Hǎikǒu (Chinese: 海口; pinyin: Hǎikǒu), is the capital and most populous city of Hainan province, China. It is situated on the northern coast of Hainan, by the mouth of the Nandu River. The northern part of the city is the district of Haidian Island, which is separated from the main part of Haikou by the Haidian River, a branch of the Nandu.
Administratively, Haikou is a prefecture-level city, comprising four districts, and covering 2,280 square kilometres (880 sq mi). There are 2,046,189 inhabitants in the built up area all living within the 4 urban districts of the city. According to the 2010 Census, the prefecture-level city of Haikou has a registered population of 2,046,189 inhabitants, 537,848 more than the population declared on the past census in 2000. The average annual population growth during the period 2000–2010 was of 3.1 percent. Most of the population of Haikou are Han Chinese (around 97.75 percent, according to the 2010 Census).
In 2017 the city’s GDP totaled 139 billion RMB, GDP per capita at 9728 USD. It has a municipal budget at 39 billion RMB. The ratio of primary, secondary and tertiary industry in Haikou is: 4.6 : 18.1 : 77.3. Main industries in Haikou include agriculture and fishery, medical care, machinery, construction, transport, conference & exhibition, and tourism, etc.
Haikou is on the northern edge of the torrid zone, and is part of the Intertropical Convergence Zone. April to October is the active period for tropical storms and typhoons, most of which occur between August and September. May to October is the rainy season with the heaviest rainfall occurring in September. Despite its location 378 km (235 mi) south of the Tropic of Cancer, the city has a humid subtropical climate (Köppen Cwa), falling just short of a tropical climate, with strong monsoonal influences. Nevertheless, the area has hot summers and warm winters, usually with high humidity. Extremes temperatures have ranged from 2.8 to 39.6 °C (37 to 103 °F).
Haikou has an extensive urban bus service. Standard fare is 1 yuan, with no bus pass, ticket, or transfer system in place. Urban minibuses operated prior to 2009, but have since been phased-out. Taxi automobiles and electric motorbikes operate throughout the city. During 2009–2010, petrol-fueled motorbike taxis were banned and seized by police at numerous checkpoints within the city.
Haikou has experienced a substantial increase in cars since the early 2000s. Traffic on main streets, once light, is now similar to other major cities, with rush hour problems that have prompted the city to expand several main roads and build a new elevated road from the west end of Guoxing Avenue to new developments west of Holiday Beach.
As of 2018, Haikou has the second best air quality among major cities nationally, preceded only by Lhasa, Tibet. However, since approximately 2009, due to an increase in the number of automobiles, there has been somewhat worsening air pollution.
Haikou was originally a port city. Today, more than half of the island’s total trade still goes through its ports. The city is home to Hainan University, which has its main campus on Haidian Island.
Haikou has sister city relationships with EU cities including Wicklow (Ireland), Sainte-Nazaire (France), Hanseatic Rostock (Germany), Ajaccio (France), Provincia di Pisa-(Italy), Gdynia (Poland), Faro (Portugal), etc.