King of the Universe is a royal title that claims complete cosmological domination. As a historical title, King of the Universe was used intermittently by powerful monarchs in ancient Mesopotamia as a title of great prestige. Equivalent titles were sometimes later used in the Greco-Roman world as honorifics for powerful rulers. The title was also applied to various deities in ancient Mesopotamian, Greek, and Roman literature. As a religious title and honorific, King of the Universe has seen continued use as a title of God and certain other figures in the Abrahamic tradition.
The etymology of the Mesopotamian title, šar kiššatim, derives from the ancient Sumerian city of Kish. In ancient Sumer, Kish was seen as having primacy over other Mesopotamian cities and was in Sumerian legend the location where the kingship was lowered to from heaven after the legendary flood. The first ruler to use the title was Sargon of Akkad (r. c. 2334–2279 BC). The title continued to be used in a succession of later empires claiming symbolical descent from Sargon's Akkadian Empire. The last known ruler to assume the Mesopotamian title was the Seleucid king Antiochus I Soter (r. 281–261 BC).
