Xerxes I (or Ahasuerus I), born around -519, died in -465, Persian "Great King", member of the Achaemenid dynasty.
During the time of his father, Darius, he participated in campaigns in Egypt (-484) and Babylon (-482).
King of Persia from -485 to -472, he was chosen by his father in preference to Artobarzanès, his older brother.
On the death of Darius in -486, he again relaunched the project of a military campaign directed against Greece. He subjugates rebellious Egypt, then resumes his father's designs against Greece (-480):he raises en masse, manages to gather more than a million men (a figure very likely exaggerated), equips at the same time a fleet of more than 1200 sails, destined to skirt the coast of the Aegean Sea, throws a bridge of boats over the Hellespont to cross this strait and in its madness, it is said, whips the sea to punish it for breaking that bridge.
He pierces the isthmus which united Mount Athos to the continent to give passage to his fleet, receives the submission of Macedonia and Thessaly, is stopped for a long time in front of the Thermopylae defended by Leonidas and does not cross them until after having lost 20,000 men. He takes Thebes, Plataea, Thespies, enters without resistance into Athens, which he delivers to the flames, but sees his fleet annihilated, by Themistocles at Salamis (-480).
He returns to Asia and leaves the command of his troops to Mardonios. The following year, his troops were again beaten at Platée and Mycale. He retired to Susa and no longer took part in subsequent battles. He began a policy of major works.
He was assassinated in -465 in a plot led by his minister Artaban. His son Artaxerxes succeeded him.
Xerxes I is equated by contemporary historians with Ahasuerus of the Bible, where he appears in the books of Esther and Esdras.