The Territory of Heard Island and McDonald Islands (HIMI) is an Australian external territory comprising a volcanic group of mostly barren Antarctic islands, about two-thirds of the way from Madagascar to Antarctica. The group's overall size is 372 km2 (144 sq mi) in area and it has 101.9 km (63 mi) of coastline. Discovered in the mid-19th century, the islands lie on the Kerguelen Plateau in the Indian Ocean and have been an Australian territory since 1947. They contain Australia's only two active volcanoes. The summit of one, Mawson Peak, is higher than any mountain in all other Australian states or territories, except Dome Argus, Mount McClintock and Mount Menzies in the Australian Antarctic Territory.

The islands are among the most remote places on Earth: They are located about 4,099 km (2,547 mi) southwest of Perth, 3,845 km (2,389 mi) southwest of Cape Leeuwin, Australia, 4,200 km (2,600 mi) southeast of South Africa, 3,830 km (2,380 mi) southeast of Madagascar, 1,630 km (1,010 mi) north of Antarctica, and 450 km (280 mi) southeast of the Kerguelen Islands (part of French Southern and Antarctic Lands). The islands are uninhabited.