Tutuila is the largest and most populous island of American Samoa and is part of the archipelago of the Samoan Islands. It is the third largest island in the Samoan Islands chain of the Central Pacific. It is located roughly 4,000 kilometers (2,500 mi) northeast of Brisbane, Australia and lies over 1,200 kilometers (750 mi) to the northeast of Fiji. It contains a large, natural harbor, Pago Pago Harbor, where Pago Pago, the capital of American Samoa, is situated. Pago Pago International Airport is also located on Tutuila. The island's land expanse is about 68% of the total land area of American Samoa. With 56,000 inhabitants, it is also home to 95% of the population of American Samoa. The island has six terrestrial and three marine ecosystems.

Tutuila has mountainous regions, the highest point of which is 653 meters (2,142 feet). The island is attractive to tourists because of its beaches, coral reefs, and World War II relics, as well as its suitability for sporting activities such as scuba diving, snorkeling, and hiking.

It is said that the name Tutuila may have been given to the island by a woman named Salaia. She named the island after a combination of the names of her parents: Tutu and Ila. Another name for the island is based on the name of Salaia herself: 'o le motu o Salaia ("the island of Salaia") or motu sā (literally, "the sacred island").

In June 1722, the Samoan Islands were first encountered by a European explorer, Jacob Roggeveen, who gave Tutuila the name Thienhoven Island. Louis Antoine de Bougainville named the island Manua or Maouna.

The Polynesians first reached Samoa around 1000 BC. By 600 BC, they had established a settlement on Tutuila at Tula. Over the centuries, the Samoans on Tutuila kept in contact with the inhabitants of the neighboring islands of Western Polynesia, Tonga, and Fiji.

Tutuila served as a place of exile for warriors and chiefs who had been defeated in the wars that ravaged much of Upolu for centuries. It was also used as a place to which Upolu rulers banished political opponents.

Around 1200 A.D., during the reign of Momo, the tenth Tuʻi Tonga, the Tongans invaded and occupied Tutuila and other Samoan Islands. Their rule lasted for nearly two centuries under five successive kings. Taʻū Island, however, claims to have been spared - an assertion not entirely implausible, as Manuka and its king held a place of honor in Tongan legend. Like most occupying powers, the Tongans soon became unpopular, and the Samoans came to believe that their divinely sanctioned leaders were destined to drive the invaders out. From this struggle emerged a new class of heroes, warriors whose successes in battle marked them as natural leaders for Samoa's eventual liberation.

During the Tongan occupation, defeated warriors and political rivals were exiled to Pago Pago, whose surrounding settlements came to serve as a kind of penal colony. In time, resentment of foreign rule grew, and under the leadership of the paramount chief Malietoa, the Samoans rose in revolt against their Tongan rulers. Fau’au of Pago Pago (Chief Fua’autoa of Pago Pago) emerged as leader of the local resistance and succeeded in expelling the Tongans from Tutuila.