An ancient country that existed in the Great Desert to the east of Amestris four hundred years before the start of the series. Despite having had a remarkably advanced society for the era, the entire population of Xerxes was mysteriously wiped out in a single night, leaving only ruins behind.

Xerxes was a relatively peaceful, thriving land despite the harsh conditions of the desert that surrounded it and, at the time of its sudden disappearance, had a population of over a million people. Xerxes appears to have had a markedly intellectual culture that fostered written language as well as philosophical and alchemical studies.