Which latitude line is located at 66.5 degrees south of the equator?

The latitude line located at 66.5 degrees south of the equator is the Antarctic Circle. This circle marks the southernmost point at which the sun can remain continuously above or below the horizon for 24 hours, which occurs during the summer and winter solstices. It plays a crucial role in understanding the Earth's climatic zones, particularly in how sunlight and temperature patterns vary in polar regions.

In contrast, the Arctic Circle is located at 66.5 degrees north of the equator and pertains to the northern hemisphere. The Tropic of Capricorn is positioned at 23.5 degrees south and is related to the sun's zenith point during the December solstice. The equator itself is at 0 degrees latitude and serves as the primary reference point for measuring other latitude lines. Thus, the Antarctic Circle is the correct choice as it relates specifically to the latitude of 66.5 degrees south.