Over 70% of the 101,991 inhabitants of the Kingdom of Tonga live on its main island, Tongatapu. Although an increasing number of Tongans have moved into the only urban and commercial centre, Nukuʻalofa, where European and indigenous cultural and living patterns have blended, village life and kinship ties continue to be important throughout the country. Everyday life is heavily influenced by Polynesian traditions and especially by the Christian faith; for example, all commerce and entertainment activities cease from midnight Saturday until midnight Sunday, and the constitution declares the Sabbath to be sacred, forever. Some Tongans are Methodists with a significant Catholic minority and a number of members of the Church of Jesus Christ of Latter-day Saints (Mormons). The official figures from the latest government census of 2006 (cf. shows that the four major church affiliations in the kingdom currently stand as follows: Free Wesleyans (38,052 or 37%); The Church of Jesus Christ of Latter Day Saints ("Mormons") (17,109 or 17%); Catholics (15,992 or 16%); Free Church of Tonga (11,599 or 11%). By their own church statistics, Mormons claim 48 percent of the population to substantiate their claim that Tonga is the most Mormon nation in the world, a phenomenon which has been remarked upon in such publications as Salon.

Tongans, Polynesian by ethnicity with a very small mixture of Melanesian, represent more than 98% of the inhabitants. The rest are European (the majority are British), mixed European, and other Pacific Islanders. There were approximately 3,000 or 4,000 Chinese in Tonga in 2001, thus comprising 3 or 4% of the total Tongan population. In 2006, Nukuʻalofa riots mainly targeted Chinese-owned businesses, leading to the emigration of several hundred Chinese.

Primary education between ages 6 and 14 is compulsory and free in state schools. Mission schools provide about 8% of the primary and 90% of the secondary level of education. State schools make up for the rest. Higher education includes teacher training, nursing and medical training, a small private university, a woman's business college, and a number of private agricultural schools. Most higher education is pursued overseas.

The Tongan language is the official language of the islands, along with English. Tongan is a Polynesian language which is closely related to Wallisian (Uvean), Niuean, Hawaiian, and Samoan. 70% of Tongan women aged 15–85 are obese. Tonga and nearby Nauru have the world’s fattest populations.