Shamash-shum-ukin, the Assyrian king of Babylon from 668-648 BCE, us the second son of the Assyrian King Esarhaddon.

His elder brother, crown prince Sin-iddina-apla had died in 672, and in his stead the third son Ashurbanipal was invested as crown prince and later king of Assyria, while Shamash-shum-ukin remained crown prince of Babylonia.

Provincial governors and vassals had to take an oath to accept this and to help the brothers gain their respective thrones in the event of Esarhaddon's death.