Shattiwaza was the brother of king Tushratta. His Hurrian name was Kili-Tešup. In the political turmoil following the death of his predecessor, the usurper Shuttarna tried to murder Shattiwaza. Shattiwaza escaped and sought refuge by the Hittite king Suppiluliuma I. He married the daughter of Suppiluliuma I and returned to Mitanni with a Hittite army. Shuttarna III who had usurped the throne in his absence was defeated and Shattiwaza installed as king of Mitanni. The events are recorded in the treaty between Suppiluliuma I and Shattiwaza.