The Gambier Islands or Mangareva Islands (French: Îles Gambier or Archipel des Gambier) are a populated (1641 people), small (30 square kilometres (12 sq mi)) group of islands, remnants of a caldera along with islets on the surrounding fringing reef, in French Polynesia, located at the southeast terminus of the Tuamotu archipelago. They 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 Gambiers are of volcanic origin with central high islands. Because of their proximity, the Acteon Group, and the nearby atolls of Maria Est, Morane, Marutea Sud and Temoe (23°20′46″S 134°28′28″W / 23.34611°S 134.47444°W / -23.34611; -134.47444), all permanently uninhabited, are sometimes included among the Gambiers.
The commune of Gambier is made up of the Gambier Islands (with uninhabited Temoe Atoll 40 km southeast of the main Gambier group), the uninhabited Acteon Group to the northwest (Matureivavao, Tenararo, Tenarunga, Vahanga), and the also uninhabited atolls of Marutea Sud, Maria Est and Morane. This group of islands and atolls covers an area of 35 km².
The Gambier Islands are a small group of islands lying between the southern tips of the Eyre and Yorke Peninsulas at the entrance to Spencer Gulf in South Australia. The islands lie within the 120 km2 Gambier Islands Group Marine Park.
By far the largest island in the group, at about 10 km2 in area, is Wedge Island. The others are North Island, South West Rock and Peaked Rocks. Except for Wedge Island, the group constitutes the Gambier Islands Conservation Park. Wedge Island is partly crown land and partly privately owned; it was used for farming for 130 years following European settlement of the region, and holds several buildings, mainly used as tourist accommodation, an airstrip, pier and a lighthouse. The waters around the islands are extensively used for commercial and recreational fishing and for recreational diving.
Australian sea lions breed on the islands, and New Zealand fur seals may haul out there. Seabirds for which the islands are important include little penguins, short-tailed shearwaters and white-faced storm petrels. Other birds recorded there include rock parrots, bush stone-curlews, peregrine falcons, ospreys and white-bellied sea eagles.