Xerxes I (ruled 486-465 BCE), also known as Xerxes the Great, was the king of the Persian Achaemenid Empire. His official title was Shahanshah which, though usually translated as `emperor’, actually means `king of kings’. He is identified as the Ahasuerus of Persia in the biblical Book of Esther (although his son, Artaxerxes I, is also a possibility as is Artaxerxes II) and is referenced at length in the works of Herodotus, Diodorus Siculus, Quintus Curtius Rufus, and, to a lesser extent, in Plutarch. Herodotus is the primary source for the story of his expedition to Greece. The name `Xerxes’ is the Greek version of the Persian `Khshayarsa’ (or Khashyar Shah), and so he is known in the west as `Xerxes’ but in the east as `Khshayarsa'.