Tukulti-Ninurta I

Tukulti-Ninurta I (lit. 'my trust is in [the warrior god] Ninurta'; reigned c. 1243–1207 BC) was a king of Assyria during the Middle Assyrian Empire. He is the first king known to use the title "King of Kings".

Source: Wikipedia — https://en.wikipedia.org/wiki/Tukulti-Ninurta_I