Xerxes I (Persian Khshayarsha) (circa 519-465 BC), king of Persia (486-465 BC), the son of Darius I and Atossa (flourished 6th century BC), daughter of Cyrus the Great. Ascending the throne upon the death of his father, he subdued a rebellion in Egypt, and then spent three years preparing a great fleet and army to punish the Greeks for aiding the Ionian cities in 498 BC and for their victory over the Persians at Marathon in 490 BC. The Greek historian Herodotus gives as the combined strength of Xerxes' land and naval forces the incredible total of 2,641,610 warriors, but it was probably between 200,000 and 300,000.
Xerxes is said to have crossed the Hellespont by a bridge of boats more than a kilometer in length and to have cut a canal through the isthmus of Mount Áthos. During the spring of 480 BC he marched with his forces through Thrace, Thessaly, and Locris. At Thermopylae 300 Spartans, under their king, Leonidas I, and 1100 other Greeks made a courageous but futile stand, delaying the Persians for ten days. Xerxes then advanced into Attica and burned Athens, which had been abandoned by the Greeks.
At the Battle of Salamís later in 480 BC, however, his fleet was defeated by a contingent of Greek warships commanded by the Athenian Themistocles. Xerxes thereupon retired to Asia Minor, leaving his army in Greece under the command of his brother-in-law, Mardonius, who was slain at Plataea the following year. Xerxes was murdered at Persepolis by Artabanus, captain of the palace guard; he was succeeded by his son Artaxerxes I (reigned 465-425 BC). Xerxes is generally identified as the Ahasuerus of the Book of Esther.