Uruk is an ancient city of Sumer and later Babylonia, situated east of the present bed of the Euphrates river, on the ancient dry former channel of the Euphrates River, some 30 km east of modern As-Samawah, Al-Muthannā, Iraq.

Uruk gives its name to the Uruk period, the protohistoric Chalcolithic to Early Bronze Age period in the history of Mesopotamia spanning c. 4000 to 3100 BCE, succeeded by the Jemdet Nasr period of Sumer proper.

Uruk plays a leading role in the early urbanization of Sumer in the mid 4th millennium BCE.

At its height c 2900 BCE, Uruk probably has 50,000–80,000 residents living in 6 km2 of walled area; making it the largest city in the world at the time.

The semi-mythical king Gilgamesh, according to the chronology presented in the Sumerian king list, rules Uruk in the 27th century BCE.

The city loses its prime importance around 2000 BEC, in the context of the struggle of Babylonia with Elam, but it remains inhabited throughout the Seleucid and Parthian periods until it is finally abandoned shortly before or after the Islamic conquest.