Antarctic Circle — World Map, the Continent It Encloses, and Geographic Facts

The Antarctic Circle is the parallel of latitude at 66°34′ S — the northernmost point in the Southern Hemisphere where the sun can stay above the horizon for 24 hours on the December solstice (the austral midnight sun) or below it for 24 hours on the June solstice (the polar night). At 15,966 km long, it crosses no countries — only the continent of Antarctica.

What is the Antarctic Circle? Definition and Geographic Facts

The Antarctic Circle is one of the five major parallels of latitude on Earth, and the southern mirror of the Arctic Circle. By definition, it is the northernmost latitude in the Southern Hemisphere where the sun can remain above the horizon for a full 24 hours — the austral midnight sun — on the December solstice, and where the sun can remain below the horizon for a full 24 hours — the polar night — on the June solstice. South of the Antarctic Circle, the durations of continuous daylight and continuous darkness extend with latitude; at the South Pole itself, the sun is up for six months and down for six months.

Antarctic Circle definition (short): the parallel of latitude at 66°34′ S marking the northern boundary of the Antarctic. Antarctic Circle latitude: -66.5606° (decimal degrees), set by 90° minus Earth's axial tilt of about 23.4°. Antarctic Circle length:15,966 km (9,920 mi) — the same length as the Arctic Circle, both small circles close to their respective poles.

Where is the Antarctic Circle on a world map? On any standard world map, the Antarctic Circle is the horizontal line near the bottom of the visible world, just above (north of) the Antarctic continent. The Antarctic Peninsula points north past the line into the Drake Passage. Most of East Antarctica and West Antarctica lie south of it. The line then loops around the continent, never touching any other landmass.

Astronomically, the Antarctic Circle defines the southern polar regions — south of the line, the sun is below the horizon during austral winter for at least one day and above it during austral summer for at least one day. Politically, it is unique: the only major line of latitude that crosses no sovereign country. The territory south of it is governed by the Antarctic Treaty System, which has frozen all national claims since 1961.

How to use this Antarctic Circle map

1. Open the world map. The dark-teal horizontal line is the Antarctic Circle at 66°34′ S (-66.5606° latitude) — 15,966 km long, the same length as the Arctic Circle. Antarctica, the only landmass the line touches, is highlighted with a translucent fill.
2. Click Antarctica to see entry/exit longitudes and length traversed. Click Antarctica on the map (or the row in the table below) to open a popup showing every longitude where the Antarctic Circle enters and exits the continent's coastline. Antarctica's deeply indented coast means the line crosses land at multiple points around the continent.
3. Read the regions, treaty, and astronomy notes. Below the map: the eight Antarctic regions on or near the line, the research stations within reach of it, the Antarctic Treaty System, and the astronomy of the austral midnight sun and polar night that define the parallel.
4. Compare with the Arctic Circle. The Antarctic Circle is the southern mirror of the Arctic Circle. Where the Arctic crosses 8 countries and 4 million people, the Antarctic crosses zero countries and only the seasonal population of research stations — the planet's only line of latitude with no sovereign territory.

Why the Antarctic Circle crosses zero countries

Every other major parallel of latitude on Earth crosses at least one sovereign country. The Equator crosses 13. The Tropic of Cancer crosses 17. The Tropic of Capricorn crosses 10. The Arctic Circle crosses 8. The Antarctic Circle crosses zero — because the only landmass it encounters is Antarctica, and Antarctica has no sovereign country.

The 1959 Antarctic Treaty, currently signed by 56 nations, freezes all territorial claims on the continent and dedicates Antarctica to peaceful scientific research. Seven countries had filed claims before 1959 — Argentina, Australia, Chile, France, New Zealand, Norway, and the United Kingdom — and several of those claims overlap. The treaty does not erase the claims, but it suspends them: as long as the treaty remains in force, no claim can be extended, no new claims accepted, and any military activity is forbidden. This makes the Antarctic Circle the only line of latitude that runs entirely through international space.

Eight Antarctic regions on or near the Antarctic Circle

Antarctica is conventionally divided into geographic and political regions. The Antarctic Circle either passes through or borders eight of them, from the warmer Antarctic Peninsula in the north to the windswept East Antarctic coast.

Research stations on or near the Antarctic Circle

About 70 research stations operate in Antarctica today, run by 30 countries; roughly 40 of them sit south of the Antarctic Circle. Below are the most notable bases on or close to the line itself, ordered south.

Climate at the Antarctic Circle: ice cap, polar plateau, and katabatic winds

Antarctica is the coldest, driest, windiest, and highest continent on Earth. Inside the Antarctic Circle, climate is classified as polar ice cap (Köppen EF) for most of the continent, transitioning to polar tundra (ET) only along the warmer Antarctic Peninsula and parts of the coast. Mean annual temperatures range from about -10 °C on the peninsula coast to -57 °C on the East Antarctic Plateau.

The polar plateau is technically a desert: annual precipitation at Vostok Station is under 20 mm — drier than the Sahara. Coastal precipitation is much higher (300-500 mm of snow per year) but still arid by global standards. The wind regime is dominated by katabatic winds — gravity-driven outflows of cold dense air pouring off the polar plateau toward the coast. At Cape Denison in Adélie Land, average wind speeds of 80 km/h have earned it the title of windiest place on Earth at sea level.

The Antarctic Convergence, an oceanic boundary at roughly 50-60° S, sits well north of the Antarctic Circle but acts as the ecological boundary of Antarctic waters. At the Convergence, cold Antarctic surface water sinks beneath warmer subantarctic water, producing a sharp temperature drop, distinctive nutrient mixing, and a sudden change in marine life — krill swarms, seabirds, and the southern bluefin tuna's polar limit all cluster around it.

The austral midnight sun and the polar night

The Antarctic Circle is defined by two astronomical phenomena: the austral midnight sun on the December solstice (around 21 December — the sun stays above the horizon for 24 hours) and the polar night on the June solstice (around 21 June — the sun stays below the horizon for 24 hours). Exactly on the line, each phenomenon happens once per year. South of the line, the durations extend with latitude; north of it, neither happens.

At 72° S (interior East Antarctica, central Antarctic Peninsula stations), the austral midnight sun lasts about 70 days and the polar night about 70 days each year. At 80° S (deep into the East Antarctic plateau), each lasts about 130 days. At the South Pole, the sun rises once a year — at the September equinox — and sets once a year — at the March equinox — making the polar day and polar night each 6 months long.

The polar night is the defining challenge of overwintering at Antarctic stations. Staff who commit to a winter season at McMurdo, Halley, or Vostok are on station for 6-12 months with no flights in or out, no daylight for weeks at a time, and temperatures that exclude external rescue. Specialised lighting protocols, vitamin-D supplementation, and psychological screening have all been developed in response. The reward is the aurora australis — the southern equivalent of the northern lights — visible above stations for hours at a time during the long polar night.

The Antarctic Circle is moving (slowly)

Like the Arctic Circle, the Antarctic Circle is not geologically fixed in latitude. Earth's axial tilt oscillates between about 22.1° and 24.5° on a 41,000-year cycle — one of the Milankovitch orbital cycles linked to ice-age timing. The Antarctic Circle latitude equals 90° minus the tilt, so it shifts in step: at minimum tilt (22.1°), the Antarctic Circle sits at 67.9° S; at maximum tilt (24.5°), it sits at 65.5° S. The total latitude range is about 270 km.

The current rate is about 14 metres per year northward(toward the equator) — the mirror of the Arctic Circle's southward drift. On human timescales this is invisible, but over millennia it has practical effects on ice extent, coastal glacier behaviour, and polar-day duration. The official Antarctic Circle latitude used on maps is updated to track the IAU value.

Crossing the Antarctic Circle: cruises, flights, and traditions

Crossing the Antarctic Circle is a recognised milestone for polar travellers. Most expedition cruises focus on the warmer Antarctic Peninsula north of the line; only longer 12-14 day “Antarctic Circle” itineraries from Ushuaia, Argentina (the closest port) reach Marguerite Bay or Crystal Sound, where the line is crossed in late January or February when sea ice retreats. Ice-strengthened expedition vessels conduct a brief ceremony on board when the ship crosses 66°34′ S.

Tourist landings inside the Antarctic Circle are limited by the Antarctic Treaty's environmental rules and by the International Association of Antarctica Tour Operators (IAATO). About 1,000-3,000 visitors per year cross the circle by sea — a small fraction of the 76,000 who visit the Antarctic Peninsula in total. Overland crossings of the line are essentially limited to scientific traverses and the South-Pole ski expeditions that depart from Hercules Inlet (-80° S) and cross every parallel south of -66.5°.

Antarctic Circle vs. Arctic Circle: a comparison

The two polar circles are geometric mirrors but ecological and political opposites. Both sit at 66.5606° latitude, both are 15,966 km long, both define the boundary of 24-hour sun and 24-hour darkness on opposite solstices. Beyond that, they diverge:

• Land vs. sea: The Arctic is a sea (the Arctic Ocean) surrounded by land. The Antarctic is a continent surrounded by sea (the Southern Ocean). Their geographies are inverted.
• Countries crossed: Arctic Circle, 8 (Norway, Sweden, Finland, Russia, USA, Canada, Greenland, Iceland). Antarctic Circle, 0.
• Population north/south of the circle: Arctic Circle, ~4 million permanent residents. Antarctic Circle, 0 permanent residents — only ~1,000-4,000 rotating researchers.
• Indigenous peoples: The Arctic has had Indigenous peoples (Sami, Inuit, Yupik, Chukchi, etc.) for thousands of years. Antarctica has no Indigenous population and was first sighted only in 1820.
• Climate range: The Arctic has a wider climate range — from subarctic taiga forest to tundra to ice cap, with the warming North Atlantic Drift moderating northwestern coasts. The Antarctic is uniformly cold, with only the Antarctic Peninsula showing significant seasonal warmth.
• Governance: The Arctic is divided among 8 sovereign countries with coastal Exclusive Economic Zones. The Antarctic is governed by the 1959 Antarctic Treaty System with no recognised sovereignty.

Related tools and resources

For the other major lines of latitude and longitude, see our companion tools: the Equator (0° latitude), Tropic of Cancer, Tropic of Capricorn, and the Arctic Circle — the northern mirror of this page.

For other geographic reference tools: find your latitude and longitude with our latitude/longitude finder, compare country sizes with the country size comparison tool (Antarctica vs. anywhere else is a striking comparison), find your antipode on the opposite side of Earth (most points north of the Arctic Circle have antipodes south of the Antarctic Circle), or check the sun position calculator for any latitude on any date.

Frequently asked questions about the Antarctic Circle