Haikou is the capital and most populous city of the Chinese province of Hainan. It is a prefecture-level city located on the northern coast of the island, situated by the mouth of the Nandu River.
The city covers an area of 2,280 square kilometres (880 sq mi) and is divided into four districts. The northern portion of the city is located on Haidian Island, which is separated from the main urban area by a branch of the Nandu River known as the Haidian River.
The built-up area of Haikou contains 2,046,189 inhabitants, all of whom reside within the city's four urban districts.