The Southern Ocean, also known as the Antarctic Ocean or South Polar Ocean, is the oceanic division completely in Earth's southern hemisphere encircling Antarctica, comprising the southernmost waters of the World Ocean south of 60° S latitude. However, the Southern Ocean's northern boundary is not precise. Instead, the Antarctica Convergence, an ocean zone which fluctuates seasonally, separates the Southern Ocean from other oceans. This dynamic, natural boundary is formed by the convergence of two circumpolar currents, one easterly flowing and one westerly.

The Southern Ocean is located in the Southern Hemisphere possessing typical depths between 4,000—5,000 meters (13,000 to 16,000 ft) deep over most of its extent with only limited areas of shallow water. The Antarctica continental shelf is generally narrow and unusually deep, its edge lying at depths up to 800 meters (2,600 ft), compared to a global mean of 133 meters (436 ft). Equinox to Equinox in line with the sun's seasonal influence, the Antarctic ice pack fluctuates from an average minimum of 2.6 million square kilometers (1.0 million mi²) in March to about 18.8 million square kilometers (7.2 million mi²) in September, more than a sevenfold increase in area.