Heard Island and McDonald Islands (abbreviated as HIMI) are barren islands located in the Southern Ocean, about two-thirds of the way from Madagascar to Antarctica, 7718 km due south of Rajapur, Maharashtra, India and approximately 4099 km west of Perth. They have been territories of Australia since 1947, and contain the only two active volcanoes in Australian territory, one of which, Mawson Peak, is the highest Australian mountain. The group's size is in area.
An American sealer, Captain John Heard, on the ship Oriental, sighted the island on 25 November 1853, en route from Boston to Melbourne. He reported the discovery one month later and had the island named after him. Captain William McDonald aboard the Samarang discovered the McDonald Islands close to Heard Island six weeks later, on 4 January 1854.
No landing was made on the islands until March 1855, when sealers from the Corinthian, led by Captain Erasmus Darwin Rogers, went ashore, at a place called Oil Barrel Point. In the sealing period from 1855-1880, a number of American sealers spent a year or more on the island, living in appalling conditions in dark smelly huts, also at Oil Barrel Point. At its peak the community consisted of 200 people. By 1880, most of the seal population had been wiped out and the sealers left the island. In all, more than 100,000 barrels of elephant seal oil was produced during this period.
There are a number of wrecks in the vicinity of the islands.
Mawson Peak is the highest Australian mountain (higher than Mount Kosciuszko), and one of only 2 active volcanoes in Australian territory, the other being McDonald Island. A long thin spit named "Elephant Spit" extends from the east of the island.
There is a small group of islets and rocks about north of Heard Island, consisting of Shag Islet, Sail Rock, Morgan Island and Black Rock. They total approximately in area.
The McDonald Islands are located to the west of Heard Island at . The islands are small and rocky and consist of McDonald Island (high), Flat Island (high) and Meyer Rock (high). They total approximately in area and, as with Heard Island, are surface exposures of the Kerguelen Plateau.
Heard Island and the McDonald Islands have no ports or harbours.
From 1947 until 1955 there were camps of visiting scientists on Heard Island (at Atlas Cove in the northwest, which was in 1969 again occupied by American scientists and expanded in 1971 by French scientists) and in 1971 on McDonald Island (at Williams Bay). Later expeditions used a temporary base at Spit Bay in the northeast, such as in 1988, 1992–93 and 2004–2005.