Nineveh (; Akkadian: 𒌷𒉌𒉡𒀀 ^URUNI.NU.A, Ninua; Biblical Hebrew: נִינְוֶה‎ Nīnəwe; Arabic: نَيْنَوَىٰ Naynawā; Syriac: ܢܝܼܢܘܹܐ, romanized: Nīnwē), also known in early modern times as Kouyunjik, was an ancient Assyrian city of Upper Mesopotamia, located in the modern-day city of Mosul 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, Persians, Scythians and Cimmerians. The city was never again a political or administrative centre, but by Late Antiquity it was the seat of a Christian bishop. It declined relative to Mosul during the Middle Ages and was mostly abandoned by the 13th century AD.

Its ruins lie across the river from the historical city center of Mosul, in Iraq's Nineveh Governorate. The two main tells, or mound-ruins, within the walls are Tell Kuyunjiq and Tell Nabī Yūnus, site of a shrine to Jonah, the prophet who preached to Nineveh. Large amounts of Assyrian sculpture and other artifacts have been excavated there, and are now located in museums around the world.