There are multiple kings with the name of Xerxes in the Bible. Keeping them straight is a bit of a puzzle. The most prominent Xerxes is Xerxes I who was king during the book of Esther. While some translations use the name Xerxes, other translations – the King James Version being the most notable – use the Persion version of the name, Ahasuerus. To further confuse the matter, this name when translated into Greek is Artaxerxes. But this is not to confuse Xerxes with Artaxerxes who are two different kings.
Suffice it to say, when Xerxes is mentioned it is likely in reference to the King of Persia who married Esther. In some translations his name is Ahasuerus. References to Artaxerxes are most likely to Xerxes’ son who followed him on the throne.
Not only is Xerxes a prominent figure in the book of Esther, but part of the book of Ezra takes place during this same time frame so he also is referenced in that book as well.