Seven countries claim parts of Antarctica: Argentina, Australia, Chile, France, New Zealand, Norway and the United Kingdom, which between them hold eight claims. Seven are pie-slice sectors running from the 60th parallel south to the South Pole, and the eighth is Norway's Peter I Island. Australia claims the most, about 42% of the continent, while Marie Byrd Land, about 1.61 million square kilometres of West Antarctica, is claimed by no one. Three claims overlap on the Antarctic Peninsula. None of these borders is enforced: the 1959 Antarctic Treaty, in force since 1961, put every claim on hold without accepting or rejecting it, and it bars any new or enlarged claim.
Because the claims are defined by meridians of longitude, the clearest way to understand them is to travel the circle. This tour starts at the pole, then runs eastward around the coast from the meridian of 20° West, crossing each boundary in turn until it returns to its starting point.
The Ceremonial South Pole, where every sector line ends
Every sector has the same southern boundary: the South Pole itself. That single point sits on the polar plateau at 2,835 metres, beside the United States' Amundsen–Scott South Pole Station, built in November 1956 as the first permanent structure at the pole. A short walk away, the Ceremonial South Pole is ringed by the flags of the twelve original Antarctic Treaty signatories. Those twelve were the countries active during the International Geophysical Year of 1957–58: the seven claimants plus Belgium, Japan, South Africa, the Soviet Union and the United States.
The northern limit of every sector is the parallel of 60° South, which is also where the Antarctic Treaty's authority ends. That parallel touches no land at all, so every claim is a wedge of ice, rock and sea whose outer edge lies in open ocean. Continental Antarctica covers about 14.2 million square kilometres, almost double the area of Australia. There is no indigenous population in any claimed sector.
20°W to 45°E: Norway's Queen Maud Land
The journey starts at 20° West, on the Caird Coast of Coats Land, where British territory ends and Norwegian territory begins. Norway annexed Queen Maud Land on 14 January 1939, five days before a German expedition aboard the Schwabenland reached the pack ice offshore. The German flights photographed about 350,000 square kilometres and dropped marker darts across what Germany called New Swabia, but Germany never made a formal claim. In 1948 Norway and Britain agreed the sector's limits as 20° West to 45° East.
Queen Maud Land covers about 2.7 million square kilometres, roughly a fifth of the continent. Its coast is a tall ice wall divided, from west to east, into the Princess Martha, Princess Astrid, Princess Ragnhild, Prince Harald and Prince Olav coasts. The original claim named no northern or southern limit. Norway set its sea edge at 12 nautical miles offshore in 2003, and only in 2015 did it formally declare that the sector runs to the pole.
Norway's only year-round base, Troll, stands on a snow-free rock slope at Jutulsessen, 235 km inland and 1,275 metres above sea level. It opened as a summer station in 1990 and has run through the winter since 2005. Troll Airfield, together with a runway at Russia's Novolazarevskaya Station, links this sector to Cape Town by intercontinental flights, and Russia works there freely under the treaty's guarantee of freedom of scientific investigation.
45°E to 160°E: Australia's two wedges and France's Adélie Land
At 45° East, on the edge of Enderby Land, the line passes into the Australian Antarctic Territory, the largest claim on the continent at about 5.9 million square kilometres. Britain transferred it to Australia in 1933, after Douglas Mawson's British Australian and New Zealand Antarctic Research Expedition proclaimed British sovereignty along the coast in 1929–31. Australia runs three permanent stations here: Mawson, founded in 1954 and the oldest; Davis, from 1957; and Casey, which replaced the old Wilkes Station and its successor in 1988. The staff number around 500 in summer and as few as 80 in winter. Only New Zealand, the United Kingdom, France and Norway recognise Australia's claim.
Travelling east along the coast, the Australian claim is interrupted at 136° East, near Pourquoi Pas Point. Here begins Adélie Land, a French sector with about 350 km of shoreline that narrows over some 2,600 km inland to the pole. It covers roughly 432,000 square kilometres. Jules Dumont d'Urville's expedition landed there on 21 January 1840, and he named it after his wife, Adèle, and Britain accepted a fixed boundary with the Australian sector in 1938. France has kept a permanent station here since 9 April 1950; today it is Dumont d'Urville Station on Île des Pétrels. At 142° East, near Point Alden, Australian territory resumes across George V Land and continues to 160° East.
160°E to 150°W: New Zealand's Ross Dependency
At 160° East the line crosses into the Ross Dependency, defined by a British Order in Council of 30 July 1923 as everything between 160° East and 150° West south of 60° South, placed under the Governor-General of New Zealand. It takes its name from James Clark Ross, who reached Victoria Land in 1841. Much of the sector is not land: it takes in most of the Ross Ice Shelf and much of the Ross Sea, along with Ross, Roosevelt, Scott and the Balleny islands.
The sector holds four permanently occupied stations. New Zealand's Scott Base stands at Pram Point on Ross Island, near Mount Erebus, just 3 km by road from the much larger US McMurdo Station. Italy's Zucchelli Station and South Korea's Jang Bogo Station are also permanently occupied here. Americans in the sector are exempt from New Zealand taxation and customs, a practical sign of how lightly any claim rests. As with Australia's sector, only Australia, France, Norway and the UK accept New Zealand's claim.
150°W to 90°W: Marie Byrd Land, the sector nobody claimed
East of 150° West the flags stop. Marie Byrd Land, named after the wife of American explorer Richard E. Byrd, is the largest unclaimed territory on Earth, about 1.61 million square kilometres including the Eights Coast. It lies east of the Ross Ice Shelf and faces the Pacific sector of the Southern Ocean. In 1939 President Franklin D. Roosevelt told the United States Antarctic Service Expedition to take steps toward claiming land, and later expeditions appear to have done so, but nothing was formalised before the treaty. The United States and Russia both say they reserve the right to make claims in future.
Offshore, in the Bellingshausen Sea about 450 km from the continent, lies the one claim that is not a wedge. Peter I Island, a glacier-covered volcano of 156 square kilometres rising to 1,640 metres, was first landed on by Norwegians on 2 February 1929. Norway annexed it in 1931 and made it a dependency in 1933. In 1967 Ecuador declared rights between 84°30′ West and 95°30′ West, overlapping both Peter I Island and the Chilean sector, a claim made after the treaty had barred new ones.
90°W to 20°W: three flags over the Antarctic Peninsula
At 90° West the Chilean Antarctic Territory begins, and from here to 20° West the claims pile on top of each other. Chile's sector runs from 90° West to 53° West under Decree 1747 of 6 November 1940, and covers about 1.25 million square kilometres, run as a commune from Puerto Williams. Britain's claim, the oldest of the three, dates from letters patent of 1908 and 1917; since 3 March 1962 it has been the British Antarctic Territory, spanning 80° West to 20° West. Argentina's sector, declared in stages between 1942 and 1946, runs from 74° West to 25° West. Between 53° and 74° West all three claims overlap, and the South Shetland Islands lie inside every one of them.
Each claimant has built on the peninsula to strengthen its case. Britain's Operation Tabarin set up a base at Port Lockroy in February 1944, and at Hope Bay in 1945. The Port Lockroy base, on Goudier Island, now keeps a museum and the world's most southerly operational post office.
Hope Bay was also where, on 1 February 1952, an Argentine shore party fired a machine gun over the heads of British survey workers, the only shots fired in anger in Antarctica; Argentina later apologised. Argentina's base there, Esperanza, later came to house families: late in 1977 a pregnant Silvia Morella de Palma was flown in, and on 7 January 1978 her son Emilio Palma was born there, the first person known to be born on the continent. Chile's equivalent is Villa Las Estrellas at Eduardo Frei Montalva Base on King George Island, settled in 1984, with about 150 people in summer and 80 in winter.
Further along lie the British stations that anchor the southern part of the peninsula and the Weddell Sea coast. Rothera, on Adelaide Island, dates from 1975 and serves as the territory's capital. Halley, founded in 1956 on the floating Brunt Ice Shelf, made the measurements that revealed the ozone hole in 1985. In December 2012 Britain named the 437,000 square kilometre triangle between its sector's boundaries and the pole Queen Elizabeth Land. Past Argentina's eastern limit at 25° West, the circle returns to 20° West and the Norwegian border where it began.
How the 1959 Antarctic Treaty froze every line
In 1955 Britain asked the International Court of Justice to settle its dispute with Argentina and Chile; both refused to take part. The deadlock ended through diplomacy instead. After the International Geophysical Year, twelve nations negotiated in Washington, and the Antarctic Treaty opened for signature on 1 December 1959 and entered into force on 23 June 1961. It set the continent aside for peaceful science and banned military activity, making it the first arms-control agreement of the Cold War.
Article IV is the clause that governs every border described above. It does not require any country to give up a claim, and it does not require any other country to recognise one. It also rules that nothing done while the treaty is in force can support or deny a claim, and it forbids new claims and enlargements. The 1991 Madrid Protocol added a ban on mining, and from 2048 any consultative party may request a review. As of 2024 the treaty had 58 parties, 29 of them with voting rights.
The claimants' stations, and the many run by non-claimants inside other countries' sectors, are covered in our guide to Antarctic research stations. The overlapping peninsula has its own geography guide, and the point where all seven wedges meet is explored further in our look at South Pole geography.