Which ocean lies entirely in the Southern Hemisphere?

The Southern Ocean is the ocean that lies entirely in the Southern Hemisphere. It encircles Antarctica and is generally defined as the waters south of 60° south latitude.

Unlike the Atlantic, Pacific, and Indian oceans, the Southern Ocean does not extend across the Equator. Its waters are linked by the Antarctic Circumpolar Current, which flows eastward around Antarctica and connects the southern portions of the world's major ocean basins.

The Southern Ocean's status has not always been universally accepted. The International Hydrographic Organization circulated a 2000 definition, but it was not formally adopted because of disagreements over ocean boundaries. National Geographic officially recognized it as a fifth ocean in 2021, while some maps and authorities use different northern limits.

It is also scientifically distinctive. Cold, dense Antarctic water helps drive global ocean circulation, and the region supports ecosystems built around krill, penguins, seals, whales, and seabirds. The Southern Ocean is sometimes called the Antarctic Ocean.