Three biblical kings had this name:
The son of Darius Hystaspes, the king named in the Book of Esther. He ruled over the kingdoms of Persia, Media, and Babylonia, “from India to Ethiopia.” This was in all probability the Xerxes of secular history, who succeeded his father Darius (B.C. 485). In the LXX version of the Book of Esther the name Artaxerxes occurs for Ahasuerus.
He reigned for twenty-one years (B.C. 486-465). He invaded Greece with an army, it is said, of more than 2,000,000 soldiers, only 5,000 of whom returned with him. Leonidas, with his famous 300, arrested his progress at the Pass of Thermopylae, and then he was defeated disastrously by Themistocles at Salamis. It was after his return from this invasion that Esther was chosen as his queen.
The father of Darius the Mede, mentioned in Dan. 9:1. This was probably the Cyaxares I, known by this name in secular history, the king of Media and the conqueror of Nineveh.
The king mentioned in Ezra 4:6, possibly the Cambyses of secular history, the son and successor of Cyrus (B.C. 529).