Which named latitude line is at about 23.5° north?

The named latitude line at about 23.5° north is the Tropic of Cancer.

It marks the northernmost latitude where the Sun can appear directly overhead. This happens around the June solstice, when Earth’s Northern Hemisphere is tilted toward the Sun. The line is therefore linked to Earth’s axial tilt, currently about 23.4°, rather than being an arbitrary cartographic boundary.

The Tropic of Cancer is one of the major circles of latitude, alongside the Equator, the Arctic and Antarctic circles, and the Tropic of Capricorn. Its southern counterpart is the Tropic of Capricorn, at roughly 23.5° south. The region between the two tropics is called the tropics.

A common mistake is to call 23.5° north the Arctic Circle. The Arctic Circle lies much farther north, near 66.5°N, and marks the approximate limit of at least one day of midnight Sun or polar night. The Tropic of Cancer slowly shifts because Earth’s axial tilt and orientation change over long periods.