Haikou (hĪˈkōˈ) [key] or Hoihow hoiˈhouˈ, city (1994 est. pop. 364,700), Hainan island, capital of Hainan prov., China. A seaport on Hainan Strait, it is the largest city on the island and an agricultural and light industrial center, with food-processing establishments, textile mills, and engineering works. The opening of the island in 1982 to foreign trade and tourism stimulated the economy, but speculation led to economic setbacks in the 1990s. Haikou has an airport.