Places starting with "X"
There are currently no countries that start with "X" in English, and common modern English place-names on Earth rarely begin with "X".
Some Earth locations associated with "X" appear in older historical spellings or earlier transliterations, but today they are usually written differently in English, so they won't show up under the letter "X" in a modern index.
To make this letter worth exploring, here are three officially named "X" locations beyond Earth — real geographic features recognized by international planetary naming authorities.
Beyond Earth: officially named "X" locations
Xanadu
Titan (moon of Saturn)
Large surface region
Authority: IAU / NASA
Xanadu is a bright, continent-sized region on Titan, identified in spacecraft imaging and radar maps. It stands out from surrounding dark dune fields and is used as a major reference area in Titan geology and mapping.
Xanthe Terra
Mars
Planetary region
Authority: IAU
Xanthe Terra is a broad classical region on Mars used in planetary mapping. It lies near major outflow channels and canyon systems, making it a well-known name in Mars geography and science literature.
Xibalba Sulcus
Mercury
Tectonic / surface feature
Authority: IAU
Xibalba Sulcus is a named system of long grooves and ridges on Mercury. Features like this record crustal deformation and help scientists interpret the planet's tectonic and thermal history.