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.
[1] Unlike its northern counterpart, almost all (97%) of it passes through open ocean.
At this latitude, daytime lasts for 15 hours, 37 minutes during the December solstice and 8 hours, 46 minutes during the June solstice for the dates in 2024.
Starting at the Prime Meridian and heading eastwards, the parallel 45° south passes through: Download coordinates as: