Tubuai or Tupua'i is the main island of the Tubuai Island group, located at , south of Tahiti. In addition to Tubuai, the group of islands include Rimatara, Rurutu, Raivavae and the uninhabited Îles Maria. They are part of the Austral Islands in the far southwest of French Polynesia in the south Pacific Ocean. Tubuai island sustains a population of 2,170 people on 45 km² of land. Due to its southerly position, Tubuai has notably cooler weather than Tahiti.
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.