Coordinates: 31°19′20″N 45°38′10″E / 31.32222°N 45.63611°E / 31.32222; 45.63611 Uruk (Cuneiform: 𒌷𒀔,^URU UNUG; Sumerian: Unug; Akkadian: Uruk; Aramaic: Erech; Hebrew: Erech; Greek: Ὀρχόη Orchoē, Ὠρύγεια Ōrugeia; Arabic: وركاء‎, Warkā') was 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 gave its name to the Uruk period, the protohistoric Chalcolithic to Early Bronze Age period in the history of Mesopotamia spanning c. 4000 to 3100 BC, succeeded by the Jemdet Nasr period of Sumer proper. Uruk played a leading role in the early urbanization of Sumer in the mid 4th millennium BC. At its height c 2900 BC, Uruk probably had 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, ruled Uruk in the 27th century BC. The city lost its prime importance around 2000 BC, in the context of the struggle of Babylonia with Elam, but it remained inhabited throughout the Seleucid and Parthian periods until it was finally abandoned shortly before or after the Islamic conquest.