The name or title applied in the Hebrew Scriptures to three different rulers.
1. The father of Darius the Mede mentioned at Daniel 9:1. It is not presently possible to make any conclusive identification of this Ahasuerus with any person in secular history.
2. The Ahasuerus of Ezra 4:6, in the beginning of whose reign an accusation was written against the Jews by their enemies, may have been Cambyses, the successor of Cyrus the conqueror of Babylon and liberator of the Jews. Cambyses reigned from 529 to 522 B.C.E.
3. The Ahasuerus of the book of Esther is believed to be Xerxes I, the son of the Persian king Darius the Great (Darius Hystaspis). Ahasuerus (Xerxes I) is shown as ruling over 127 jurisdictional districts, from India to Ethiopia. The city of Shushan was his capital during major portions of his rule.—Es 1:1, 2.
In the book of Esther the regnal years of this king apparently are counted from the coregency with his father Darius the Great. This would mean that Xerxes’ accession year was 496 B.C.E. and that his first regnal year was 495 B.C.E. (See PERSIA, PERSIANS.) In the third year of his reign, at a sumptuous banquet, he ordered lovely Queen Vashti to present herself and display her beauty to the people and princes. Her refusal caused his anger to flare up, and he dismissed her as his wife. (Es 1:3, 10-12, 19-21) In the seventh year of his reign he selected Esther, a Jewess, as his choice out of the many virgins brought in as prospects to replace Vashti. (Es 2:1-4, 16, 17) In the 12th year of his reign he allowed his prime minister Haman to use the king’s signet ring to sign a decree that would result in a genocidal destruction of the Jews. This scheme was thwarted by Esther and her cousin Mordecai, Haman was hanged, and a new decree was issued, allowing the Jews the right to fight their attackers.—Es 3:1-11; 7:9, 10; 8:3-14; 9:5-10.
Subsequently, “King Ahasuerus proceeded to lay forced labor upon the land and the isles of the sea.” (Es 10:1) This activity fits well with the pursuits of Xerxes, who completed much of the construction work his father Darius initiated at Persepolis.
Xerxes I also appears to be the “fourth [king]” mentioned at Daniel 11:2, the three preceding ones being Cyrus the Great, Cambyses II, and Darius Hystaspis. While seven other kings followed Xerxes on the throne of the Persian Empire, Xerxes was the last Persian emperor to carry war into Greece, whose rise as the dominant world power is described in the verse immediately following.—Da 11:3.