Ur (Sumerian: Urim; Sumerian Cuneiform: 𒋀𒀕𒆠 URIM₂^KI or 𒋀𒀊𒆠 URIM₅^KI; Akkadian: Uru) was an important city-state in ancient Sumer located at the site of modern Tell el-Muqayyar in Iraq's Dhi Qar Governorate. Once a coastal city near the mouth of the Euphrates on the Persian Gulf, Ur is now well inland, south of the Euphrates on its right bank, 16 kilometres (9.9 mi) from Nasiriyah.

The city's patron deity was Nanna, the Sumerian moon god, and the name of the city is in origin derived from the god's name, URIM₂^KI being the classical Sumerian spelling of LAK-32.UNUG^KI, literally "the abode (UNUG) of Nanna (LAK-32)".

The site is marked by the ruins of the Great Ziggurat of Ur, which contained the shrine of Nanna, excavated in the 1930s. The temple was built in the 21st century BC (short chronology), during the reign of Ur-Nammu and was reconstructed in the 6th century BC by Nabonidus. The ruins cover an area of 1,200 metres (3,900 ft) northwest to southeast by 800 metres (2,600 ft) northeast to southwest and rise up to about 20 metres (66 ft) above the present plain level.