The island is ringed by a lagoon formed by an encircling coral reef. A break in the reef that enables passage for ships is located on the north side of the island. Tubuai has two volcanic domes, with its highest point, Mt Taita'a, being 422 meters. Six or seven islets called motus lie along the reef rim that encircles the island. These were described in the late 1700s as having an abundance of Toa trees, which the native islanders used in housebuilding and in making war clubs and spears due to the wood's density.
The island has been inhabited for more than 2000 years. In the ancient past a road was built that encircled the island. There exists on the island today the stone ruins of a “great number of structures, house platforms, marae complexes, and cemeteries...” According to David Stanley's South Pacific Handbook:
"The Austral islands were one of the great art areas of the Pacific, represented today in many museums. The best-known artifacts are tall sharkskin drums, wooden bowls, fly whisks, and tapa cloth."
Tubuai was first viewed by Europeans when it was mapped by Captain James Cook in 1777, although his party did not disembark. Cook discovered the island's name, "Toobouai", from the natives who surrounded his ship in their canoes (a Tahitian named Omai, who was part of Cook's group, translated).
The next Europeans to arrive were the mutineers of the HMS Bounty in 1789. Mutineer Fletcher Christian, in looking for an island on which to permanently hide, had "scoured" Bligh's maps and nautical charts and decided on Tubuai.
Upon arrival at Tubuai, a conflict arose while the mutineers were still on their ship and several islanders were killed in their canoes. The site of this event in the lagoon on the north side of the island is called Baie Sanglant (Bloody Bay).
Mutineer James Morrison wrote: "The Island is full of Inhabitants for its size and may Contain 3000 souls." After only ten days on the island, the mutineers sailed for Tahiti to get women and livestock in which they were only nominally successful. When they returned to Tubuai they built a fort on the northeast part of the island at Ta'ahueia, manned with cannon and swivel gun which they named Fort George. The mutineer leader, Fletcher Christian, knew that settling on Tahiti was sure to mean the mutineers' eventual discovery and arrest, so despite being viewed as intruders, Christian was reluctant to view permanent settlement on Tubuai as unfeasible. Christian favoured using diplomacy over time to eventually obtain wives, but many of the other mutineers insisted on raiding parties to take wives by force. The islanders of Tubuai did not want to allow their women to stay at the mutineer camp, or to allow them to become wives. They also were not disposed to trade food. It was not long before armed parties of mutineers started burning houses and desecrating marae during skirmishes to obtain women. More battles ensued and more natives were killed. One mutineer, heavily tattooed Thomas Burkett (who was later tried and hanged in England for mutiny) was speared in the side by one of the islanders during one of the skirmishes. After only two months since their first arrival on Tubuai the mutineers left for good.
Increased contact with Europeans also meant more exposure to diseases to which the islanders had no immunity. This proved particularly devastating to the population of Tubuai. At some point during the 30 years from when the mutineers left the island on September 17, 1789, and the early 1820s when accounts by Christian missionaries began to be recorded, the population that was estimated by the mutineer Morrison to be 3000 was now reduced to no more than 300 people. One Protestant minister when visiting a congregation on Tubuai on January 3, 1824, wrote that several islanders were still suffering from a devastating illness. He described the symptoms and noted that several hundred had died within the previous four years.
Tupua'i is located at 23°23′00″S 149°27′00″W / 23.38333°S 149.45000°W / -23.38333; -149.45000, just above the Tropic of Capricorn. The island is at the centre of Austral Islands, located 195 km from Ra'ivāvae, 210 km from Rurutu, 700 km from Rapa Iti and 640 km south of Tahiti.
It consists of two former sets of volcanic peaks on Mount Taita'a (422 m (1,385 ft)) which are separated by the collar of Huahine (35 m (115 ft)). Its area is 45 square kilometres (17 square miles), surrounded by a large lagoon (the largest of the Austral Islands).
The barrier reef that surrounds it in effect creates a lagoon of 85 square kilometres (33 square miles), an area almost double that of the island. It sometimes reaches 5 kilometres (3.1 miles) wide. Its depth is low, leading to a characteristic colour of turquoise or jade. For a large part, its depth is around 6 metres (20 feet). However, it can reach up to 25 metres (82 feet) in some parts of the south-east. The waters are constantly replenished via a rather strong and fairly constant ocean current, contributing to the preservation of the lagoon habitat and the health of the coral in the reef. The generally cooler waters and until recently very low pollution have also helped sustain this environment.
Many small streams run through the island, though they often empty into swamps rather than the sea. These swamps represent a fairly large portion of the island. Only the river Vaiohuru has any real flow.
Eight offshore islands motu in Tahitian, surround the main island (with an diitional 0.4 sqkm):
The islets above are listed in clockwise direction from the north of the island. The last two islands are often submerged and hence not visible.
The motu 'Ōfa'i is itself the only island that has not formed through the coral because it is only composed of basalt, hence its name. It is also the only outcrop of volcanic land other than the main island.
The climate of Tubuai is cooler than Tahiti, with temperatures averaging 20–25 °C (68–77 °F). The climate is rather temperate although it can be quite tropical for a large part of the year. The lowest temperature measured on the island was 9.2 °C (48.6 °F) on 31 August 1951. The highest was 32.7 °C (90.9 °F) on 25 March 1980. The lagoon waters typically reach 26 °C (79 °F) in summer but only drop a few degrees in winter.
The rainfall is about 2000 mm per year with about 1700 mm per year for the years 2006 and 2007. The highest recorded rainfall 2839 mm in 1962 and the lowest was 1186 mm 1952. The record for rainfall in a day is in turn 191 mm on 23 April 1942.
Hours of sunlight is about average for the Australs and is around 1970 hours per year, one of the lowest levels in Polynesia. The humidity is lower in contrast to Tahiti in the order of a few percent, mainly due to its higher latitude and its lower altitude (thus retaining fewer clouds).
The trade winds coming from South-East are the prevailing winds. Those coming from the North or Northwest are synonymous with a change towards more sunny days. The maximum recorded wind speeds, however, never exceeded 45 m/s.
The island has also been the scene of several cyclones, though they are not very frequent and are often weakened before reaching landfall (as with Cyclone Meena in 2004). However, much bigger cyclones occasionally hit the island. As such, on 5 February 2010, Tupua'i found itself in the path of Cyclone Oli with winds averaging 160 km/h (gusting nearly 220 km/h).
Since the 1990s, the island's population has stabilised to approximately 2,000 inhabitants.
Evolution of the population of Tupua'i since its discovery:
Tubuai is the administrative capital of the Austral Islands, and the commune consists solely of this one island, including the six or seven motus surrounding it. Tubuai was annexed by France in 1881. The commune itself consists of the following associated communes: