The summit of volcanic (volcano) undersea mountains forms the two roughly parallel chains of the Tongan islands. Most of the islands of the western chain are classified as high islands, because they have been raised well above sea level by repeated volcanic activity. Four of them are still active volcanoes. Some of the islands composed of lava formed by shield volcanoes, such as Late and Kao, have a hard cone-shaped surface that is not easily eroded. Others, such as Fonuafoʿou (Falcon Island), were formed by more explosive volcanoes, and their surfaces, composed of ash and pumice, erode readily. Fonuafoʿou has arisen and disappeared repeatedly, owing to its cycles of eruption and erosion.

The low islands of the eastern chain have been capped by coral polyps and foraminifera (marine organisms that have calcareous shells), which build coral rock and limestone reefs. The continuing growth of coral counteracts the sea's erosion of the reefs and the islands enclosed by them. A protective reef surrounds Tongatapu Island; many islands in the Vavaʿu Group lack such protection and are shrinking.

Tongatapu Island, a raised atoll in the Tongatapu Group, with an area of 100.6 square miles (260.5 square km), is the largest and most densely populated island in Tonga. The highest point in Tonga, 3,389 feet (1,033 metres), is on Kao Island in the Haʿapai Group. ʿEua Island (Euaʿ) (Tongatapu Group) has an old volcanic ridge rising to 1,078 feet (329 metres) above sea level. The Vavaʿu Group has hills ranging from 500 to 1,000 feet (150 to 300 metres), and Late Island, in its western volcanic chain, rises to 1,700 feet (518 metres). Vavaʿu Island has a fine, large landlocked harbour. The effects of natural erosion are particularly vivid in Vavaʿu. Rainwater reacting with the carbon dioxide in vegetation acquires acidic properties and dissolves coral and limestone rock, thereby forming caves. The constant action of the waves has created the sheer cliffs and sandspits of Vavaʿu and Nukuʿalofa. There are no rivers in Tonga, although ʿEua and Niuatoputapu have creeks.

Tonga has a semitropical climate except in the northernmost islands, where truly tropical conditions prevail. Temperatures range between 60 and 70 °F (16 and 21 °C) in June and July and reach 80 °F (27 °C) in December and January. The mean annual humidity is 77 percent. The mean annual precipitation varies from 64 inches (1,620 mm) in the Haʿapai Group to 97 inches (2,450 mm) on Niuafoʿou. Humidity increases as the distance from the Equator lessens. The northern islands, which are closest to the Equator, are particularly vulnerable to typhoons, which generally occur between December and April.

The well-drained, fertile soils of Euaʿ, Kao, Tofua, and Late islands and the slopes and hilltops of Vavaʿu support original forests. ʿEua has the greatest number and variety of trees, and the ridge on the eastern side is a forest reserve. The fast-growing toi and the tavahi constitute a majority of the tree cover on ʿEua. The sandy, rocky, dry soils of the coasts and the direct exposure there to strong winds and salty spray create unfavourable conditions for coastal vegetation. To conserve moisture, plants near the shore have small waxy or hairy leaves. Tidal sand and mudflats have swampy areas that support mangroves. Behind the mudflats, trees with buttress roots, such as the lekileki, sometimes grow.

Tonga's land birds include doves, rails, starlings, kingfishers, and many others. The red-breasted musk parrot and the blue-crowned lory, considered by some to be the most beautiful birds in the Pacific, inhabit ʿEua. Island cliffs serve as homes for red-tailed and white-tailed tropic birds. Among the native birds of Niuafoʿou Island is the incubator bird. The common reef heron is a native shorebird. Transient species include golden plovers, wandering tattlers, long-billed curlews, and bar-tailed godwits. Tongan waters attract several varieties of seabirds such as noddies, terns, frigate birds, and mutton birds. The village of Kolovai on Tongatapu Island is home to a colony of flying foxes (flying fox) (Pteropus tonganus, a type of Old World fruit bat). The bats cling to large trees by day and fly at night to forage for food.

Tongans (Tonga) are closely related to Samoans and other Polynesians in culture, language, and racial makeup. Nearly the entire population claims an original Polynesian ancestry, with a small amount of Melanesian influence through contact with Fiji. Intermarriage with Europeans has become more common, especially as a result of the increasing out-migration of Tongans since the 1970s. Religion is an important aspect of Tongan society, and most Tongan families are members of a Christian church. About two-fifths belong to the Free Wesleyan (Methodist) Church; there are smaller numbers of Mormons and Bahāʾīs; and the remainder belong to smaller, mostly Protestant, denominations. The Tongan language is taught in primary schools and is the official language, in addition to English, which is studied as a second language.

Most of the Tongan population lives in the three major island groups, and nearly three-fourths live on Tongatapu Island. The urban population has been steadily growing and now accounts for about one-third of the total population. Many Tongans migrate overseas, in particular to the United States and New Zealand.

The majority of the population lives in villages. Traditional structures are called fale; they are rectangular in shape and have thatched or corrugated tin roofs and sides made of woven coconut leaves, reeds, or timber. Some Tongans reside in South Seas colonial-style wooden homes with gingerbread trim and exterior walls in pastel shades.

Agriculture is the mainstay of the Tongan economy. Squash, coconuts, bananas, and vanilla beans constitute the main cash crops, and other important crops include yams, taro, cassava, corn (maize), watermelons, pineapples, breadfruit, limes, and tomatoes. All land is essentially owned by the Tongan monarchy, but large estates have been divided among the country's nobles. Land is parceled out to peasant proprietors: traditionally, every male age 16 or over was entitled to an allotment of 7.5 acres (3 hectares) of land for cultivation; more recently, population growth has reduced the size of actual allotments in many places. Timber production, livestock raising, and fishing also contribute to Tonga's economy. Many of Tonga's products are consumed domestically, but imports—mainly from New Zealand, Australia, Fiji, and the United States—form the bulk of the goods consumed in the country. Food and beverages account for the largest category of imports, in terms of value.

Manufactures include concrete products, construction and transportation equipment, furniture, clothing, food products, and various small handicrafts. A small mining industry quarries coral and sand. Crop processing and marketing have been undertaken by cooperative societies. Remittances from Tongans working overseas—especially in New Zealand, the United States, and Australia—and tourism have both contributed significantly to the growth of the Tongan economy.

About one-fourth of Tonga's road network consists of paved all-weather roads, almost all of which are located on the two largest islands; the remaining roads are of dirt or coral. Tonga has no railroad. Nukuʿalofa and Neiafu are ports used for external shipping. Copra and bananas are exported from Pangai. Regular international air service to New Zealand, Fiji, Australia, Samoa, American Samoa, Niue, and Hawaii (Honolulu) is available from Fuaʿamotu International Airport on Tongatapu. Domestic flights are serviced by airports on ʿEua, Haʿapai, Vavaʿu, Niuafoʿou, and Niuatoputapu.

Education is free for all Tongans, and attendance is compulsory between ages 5 and 14. The government runs primary, secondary, and vocational training schools, including a teacher-training college, and the government and many Commonwealth countries offer scholarships to help Tongans pursue higher education abroad. Some primary and secondary schools as well as vocational institutions are run by churches. The University of the South Pacific operates an extension centre in Nukuʿalofa. The private ʿAtenisi Institute (1975) offers secondary, undergraduate, and graduate studies in the liberal arts. Tongans receive free dental and medical treatment. Although the general health of the population is adequate, rates of noncommunicable diseases related to obesity (such as diabetes, hypertension, and heart disease) have risen steadily since the 1970s. Family planning aids are disseminated with the help of the United Nations and New Zealand.

Carving was traditionally done by men, but the craftsmanship was inferior to that of other Polynesians, such as the Maori of New Zealand. Carving and other traditional crafts of higher quality have been produced, however, in response to the demands of the tourist market. Women manufacture tapa cloth from bark and weave mats and baskets from several varieties of pandanus leaves. Traditional dancing (dance) is an important part of national ceremonies and local village festivities. In the popular paddle dance, called meʿetuʿupaki, dancers carry paddle-shaped boards painted or carved with abstractions of the human body. Other popular dances include the kailao, a war dance; the lakalaka and the maʿuluʿulu, dances performed by standing and seated groups, respectively, and accompanied by densely polyphonic singing; and the tauʿolunga, an individual dance accompanied by singing. An oral tradition persists in Tongan villages in the form of proverbs, religious epics, genealogies, poetry, fables, and myths.

Although some islands were visited by the Dutch navigators Jakob Le Maire and Abel Janszoon Tasman (Tasman, Abel Janszoon) in 1616 and 1643, respectively, effective European contact dates from Capt. James Cook (Cook, James)'s visits between 1773 and 1777. Cook called the Tonga islands the Friendly Islands, because the native inhabitants provided him with necessary supplies and gave him a warm welcome. The London Missionary Society and a mission of Methodists made unsuccessful attempts to introduce Christianity to Tonga in 1797 and 1822, respectively. A renewed attempt by the Methodist mission in 1826 was successful, and a Roman Catholic mission was established by the Marists in 1842. Between 1799 and 1852 Tonga went through a period of war and disorder. This was finally ended by Taufaʿahau, who was converted to Christianity in 1831 by the Methodist missionaries. He became Tuʿi Kanokupolu and subsequently took the title King George Tupou I in 1845. During the king's long reign (1845–93), Tonga became a unified and independent country with a modern constitution (1875), legal code, and administrative structure. With Taufaʿahau as its most important convert, Christianity spread rapidly. In separate treaties, Germany (1876), Great Britain (1879), and the United States (1888) recognized Tonga's independence. George I was succeeded by his great-grandson George II, who died in 1918. During his reign the kingdom became a British (British Empire) protectorate (1900) to discourage German advances. Under the treaty with Great Britain (amended in 1905), Tonga agreed to conduct all foreign affairs through a British consul, who had veto power over Tonga's foreign policy and finances. George II was followed by Queen Salote Tupou III, who ruled from 1918 to 1965. She was succeeded upon her death in 1965 by her son Prince Tupoutoʿa Tungi, who had been Tonga's prime minister since 1949. He ruled as King Taufaʿahau Tupou IV.

In 1970 Tonga regained full control of domestic and foreign affairs and became a fully independent nation within the Commonwealth. A pro-democracy movement took shape in the late 20th century, and, from the 1990s, reform advocates won significant representation in the legislature. The government, however, resisted change. Pro-democracy leaders, including ʿAkilisi Pohiva, a member of the legislature, were occasionally arrested and imprisoned.

From 1983 to 1991, despite domestic and international objections, the government sold some 6,600 Tongan passports to foreign nationals. The revenue from the sale—purportedly some $30 million—was invested in a trust fund that in the late 1990s came under the control of an American businessman, Jesse Bogdanoff. However, by 2001 the fund had lost nearly its entire value to risky investments; a Tongan lawsuit against Bogdanoff in U.S. courts was settled in 2004 for only a fraction of the loss.

As the reform movement gained momentum, some in the legislature and in the royal family were sympathetic. The government, however, responded by attempting to further solidify its authority. In 1999 the first indigenous broadcast television service, government-owned Television Tonga, was established. A newspaper critical of the government and the monarchy, Taimi ʿo Tonga, was banned at various times for allegedly being seditious. The legislature amended the constitution in 2003 to increase governmental control over the media, despite an earlier large-scale public demonstration in Nukuʿalofa against the changes; the Supreme Court later invalidated the amendments. From July to September 2005, in the first national strike in the country's history, thousands of public service workers struck successfully for greater pay equity.

Following his accession to the throne, King George Tupou V began divesting himself of ownership in many of the state assets that constituted much of the wealth of the monarchy. This process was completed prior to his coronation in August 2008. At the same time, the king announced the cession of much of the monarchy's absolute power; henceforth, most of the monarch's governmental decisions, except those relating to the judiciary, would be made in consultation with the prime minister.

Bantu-speaking people who inhabit the southern portion of Zambia and neighbouring areas of northern Zimbabwe and Botswana. Numbering more than one million in the early 21st century, the Tonga are concentrated along the Zambezi Escarpment and along the shores of Lake Kariba. They are settled agriculturists who grow corn (maize) primarily for subsistence but also for limited commercial purposes. The vast majority of Tonga live in small, dispersed villages; they are the only one of Zambia's major ethnic groupings whose wealth and power are founded upon rural, agricultural activities as opposed to urban pursuits.

Descent and land inheritance are reckoned among the Tonga along matrilineal lines, and a newly married couple go to live near the bride's relatives. They attribute marked importance to spirits associated with rainfall, and thus rainmakers are prominent in Tonga society.

Before the British (British Empire) colonization of what is now Zambia, the Tonga were loosely organized into a number of matrilineal clans that had neither leaders nor defined political functions. These clans were subdivided into numerous small lineages that controlled property and arbitrated disputes among their members. The British appointed village chiefs from among prominent local Tongas, and gradually this network of local officials coalesced into a single, unified political structure comprising a hierarchy of chiefs. Both the ethnic identity and political organization of the Tonga are thus ultimately the products of British attempts to administer them.

In the early 21st century the Tonga proper constituted about one-eighth of Zambia's population, making them the second largest ethnic group (after the Bemba) in the country.