The Gambier Islands (Îles Gambier or Archipel des Gambier) are an archipelago in French Polynesia, located at the southeast terminus of the Tuamotu archipelago. They cover an area of , and are made up of the Mangareva Islands, a group of high islands remnants of a caldera along with islets on the surrounding fringing reef, and the uninhabited Temoe atoll, which is located 45 km (28 mi) south-east of the Mangareva Islands. The Gambiers are generally considered a separate island group from Tuamotu both because their culture and language (Mangarevan) are much more closely related to those of the Marquesas Islands, and because, while the Tuamotus comprise several chains of coral atolls, the Mangareva Islands are of volcanic origin with central high islands.
Administratively, the Gambier Islands are inside the commune of Gambier, which also includes several atolls in the Tuamotu Archipelago. The town hall (mairie) of the commune of Gambier is located on Mangareva, in the Gambier Islands.
The population of the Gambier Islands was 1,431 people at the 2017 census, all living in the Mangareva Islands.
Ethnologist Kenneth P. Emory of the Bishop Museum in Honolulu assumed that the Gambier Islands, like the other islands of East Polynesia, were colonized from the Marquesas. However, it is now more likely that settlement originated in the Society Islands around 1000 A.D. There is archaeological evidence that the islands of Mangareva, Taravai, Agakauitai, Akamaru, Aukena and Kamaka were colonized by Polynesians in protohistoric times. The social form was a strictly stratified tribal society, with constant inter-clan warfare and intermittent food shortages; cannibalism was not unknown. There is evidence that, shortly before European influence, unrest was taking place that led to turmoil and civil war between the social classes. This social upheaval may have greatly facilitated the conquest of the archipelago by King Pomaré II of Tahiti in the early 19th century.