45th parallel south
It is the line that marks the theoretical halfway point between the equator and the South Pole. The true halfway point is 16.2 km (10.1 mi) south of this parallel because Earth is not a perfect sphere, but bulges at the equator and is flattened at the poles.
Unlike its northern counterpart, almost all (97%) of it passes through open ocean. It crosses the South Atlantic Ocean, the Indian Ocean, Australasia (New Zealand and just south of Tasmania), the Southern Ocean, and Patagonia.
Starting at the Prime Meridian and heading eastwards, the parallel 45° south passes through: