A mountainous planet colonized by descendants of Earth by the 30th century. It is a member of the United Planets. Despite the fact the planet is located on the rim of the United Planets and often suffers from black outs, it has several advances in science and several costumed protectors.
In all continuities, it is the homeworld of the Legionnaire Star Boy and the hero Atmos. In the postboot continuity, Xanthu had its own team of super-heroes called the Uncanny Amazers. Atom'X, Insect Queen, Kid Quantum, Kid Quantum II, Konk and Monstress were all Xanthu natives.