Larsa (lär´sə), ancient city of S Babylonia, in modern Iraq, 30 mi (48 km) NW of An Nasiriyah. It was the biblical Ellasar (Gen. 14.1). When the last king of the third dynasty of Ur was overthrown (c.1950 BC) by the Elamites and Amorites, the cities of Isin and Larsa were rivals for hegemony in Mesopotamia. In 1763 BC, Hammurabi defeated Larsa and succeeded in uniting Babylonia under his power. The city was dedicated to the sun god, Shamash. Temple libraries and important documents have been found in the ruins.