Tonga, officially the Kingdom of Tonga, an archipelago in the South Pacific Ocean, comprises 169 islands, 36 of which are inhabited, and stretches over a distance of about 800 kilometers in a north-south line. The islands that constitute the archipelago lie south of Samoa, about one-third of the way from New Zealand to Hawaii.

Tonga, the only sovereign monarchy among the island nations of the Pacific Ocean, has the distinction of being the only island nation in the region to have avoided formal colonization.

By the 12th century Tongans had a reputation across the central Pacific, leading some historians to speak of a 'Tongan Empire'. In the 15th century and again in the 17th, civil war erupted. In 1845 the ambitious young warrior, strategist, and orator Tāufaʻāhau united Tonga into a kingdom.

Tonga became a protected state under a Treaty of Friendship on 18 May 1900, when European settlers and rival Tongan chiefs tried to oust the second king. Within the British Empire, which posted no higher permanent representative on Tonga than a British Consul (1901-1970), it was part of the British Western Pacific Territories from 1901 until 1952. Although under the protection of Britain, Tonga is the only Pacific nation never to have given up its monarchical government.

The Treaty of Friendship and Tonga's protectorate status ended in 1970. Tonga joined the Commonwealth of Nations in 1970 (atypically as an autochthonous monarchy, that is one with its own hereditary monarch rather than Elizabeth II), and the United Nations in September 1999.