Tonga is a country in the South Pacific Ocean in Oceania. Proximate countries include Fiji, Vanuatu, and Tuvalu. Tonga is an archipelago of 170 islands mainly raised by coral, but some are volcanic. The government system is a constitutional monarchy; the chief of state is the king, and the head of government is the prime minister. Tonga has a mixed economic system in which there is a variety of private freedom, combined with centralized economic planning and government regulation.