The Southern Ocean (also known as the Great Southern Ocean, Antarctic Ocean, South Polar Ocean, and Austral Ocean) comprises the southernmost waters of the World Ocean, generally taken to be south of 60°S latitude and encircling Antarctica.

As such, it is regarded as the fourth-largest of the five principal oceanic divisions (after the Pacific, Atlantic, and Indian Oceans, but larger than the Arctic Ocean). This ocean zone is where cold, northward flowing waters from the Antarctic mix with warmer subantarctic waters.

Geographers disagree on the Southern Ocean's northern boundary, and some even its existence—considering the waters part of the Pacific, Atlantic, and Indian Oceans instead. Others regard the Antarctic Convergence, an ocean zone which fluctuates seasonally, as separating the Southern Ocean from other oceans, rather than the 60th parallel. Australian authorities regard the Southern Ocean as lying immediately south of Australia.
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