Tongan is a member of the Polynesian branch of the Austronesian languages spoken by about 95,000 people mainly in Tonga. It is also spoken in American Samoa, Australia, Canada, Fiji, New Zealand, Niue, the USA and Vanuatu. It closely related to Niue, Wallisian and Samoan.
Tongan was first written by missionaries in the early 19th century using a number of different spelling systems. The currect system was promulgated by the Privy Council of Tonga in 1943.
source
wikipedia.org,
omniglot.com &
ethnologue.com