 The Kingdom of Tonga is an archipelago of 169 islands ( 36 are inhabited by about 100 @,@ 000 people ) that is located in the South Pacific Ocean to the far east of Australia . Initially known as the " Friendly Islands " by explorers , The islands of Tonga united under a single monarchy in 1845 , and devised a constitution to restrain the monarchy in 1875 . It is the only nation in the South Pacific that has neither been formally colonized nor had its original government dissolved , although it became a protectorate of the United Kingdom on 1900 . Tonga renounced British protection in 1970 and , as of 2012 , was the only monarchy in the Pacific Ocean . 
