Nineveh ( NIN-iv-ə; Akkadian: , ^URUNI.NU.A, Ninua; Biblical Hebrew: נִינְוֵה, Nīnəwē; Arabic: نِينَوَىٰ, Nīnawā; Syriac: ܢܝܼܢܘܹܐ, Nīnwē), also known in early modern times as Kuyunjiq for its northern part, was an ancient Assyrian city of Upper Mesopotamia, located in the modern-day city of Mosul (itself built out of the Assyrian town of Mepsila) in northern Iraq. It is located on the eastern bank of the Tigris River and was the capital and largest city of the Neo-Assyrian Empire, as well as the largest city in the world for several decades. Today, it is a common name for the half of Mosul that lies on the eastern bank of the Tigris, and the country's Nineveh Governorate takes its name from it.

It was the largest city in the world for approximately fifty years until the year 612 BC when, after a bitter period of civil war in Assyria, it was sacked by a coalition of its former subject peoples including the Babylonians, Medes, and Scythians. The city was never again a political or administrative centre, but by Late Antiquity it was the seat of an Assyrian Christian bishop of the Assyrian Church of the East. It declined relative to Mosul during the Middle Ages and was mostly abandoned by the 14th century AD after the massacres and dispersal of Assyrian Christians by Tamurlane.

Its ruins lie across the river from the historical city center of Mosul. The two main tells, or mound-ruins, within the walls are Tell Kuyunjiq and Tell Nabī Yūnus, site of a shrine to Jonah. According to the Hebrew Bible and the Quran, Jonah was a prophet who preached to Nineveh. Large numbers of Assyrian sculptures and other artifacts have been excavated from the ruins of Nineveh, and are now located in museums around the world.