Haikou is the capital and most populous city of Hainan province in China. It is a prefecture-level city that covers an area of 2,280 square kilometres (880 sq mi) and serves as a major urban center for the region.
The city is situated on the northern coast of Hainan by the mouth of the Nandu River. Its geography includes Haidian Island in the northern part of the city, which is separated from the main urban area by the Haidian River, a branch of the Nandu River.
Administratively, Haikou comprises four districts. The built-up area of the city has a population of 2,046,189 inhabitants, all of whom reside within these four urban districts.