In southeastern Iraq, (modern Tall Sankarah), about 25 miles (40 km.) west of modern an-Nasiriyah.

Larsa (possibly the Biblical Ellasar, Genesis 14:1), was an important city of ancient Mesopotamia. It was located in the south. It lay 15 miles southeast of the ruin mounds of Uruk (biblical Erech), near the east bank of the Shatt-en-Nil canal (modern day southern Iraq). Larsa is mentioned in Sumerian inscriptions as early as the time of Ur-Gur, 2700 or 2800 BC, who built or restored the ziggurat (stage-tower) of E-Babbar, the temple of Shamash.

Larsa first became a formidable force in Mesopotamia during the Old Babylonian period (c. 2000-1600 BCE). After the Third Dynasty of Ur collapsed, a power vacuum arose that many of the larger city-states hurried to fill. In southern Mesopotamia, an official of Ibbi-Sin, the last king of the Third Dynasty of Ur, relocated from Ur to Isin and set up a government there that purported to follow in the Third Dynasty's footsteps. This king, Ishbi-Erra (c. 2017-1985), helped recapture some of the Dynasty's previous land, including the culturally symbolic and commercially crucial towns of Ur and Uruk.

Ishbi-Erra also regained power over the province of Lagash, of which Larsa was a part. The subsequent Isin rulers appointed governors to rule over Lagash; one such governor was an Amorite named Gungunum. He eventually broke with Isin and established an independent dynasty in Larsa. To legitimize his rule and deliver a blow to Isin, Gungunum captured the city of Ur. As the main center of trade with the Arab-Persian gulf, Isin lost an enormously important portal to a profitable trade route, not to mention a city with much cultic significance.

Beyond these few details, the precise reason for Gungunum's break with Isin are largely unknown. One group of scholars theorizes that Isin's internal problems were to blame; it does seem that Isin's rulers allowed the once burgeoning irrigation and agricultural systems to wane. It is possible this was due to sheer neglect, but there is evidence that acquiring access to water in this arid region posed quite a problem for most of southern Mesopotamia in this period.

Gungunum's two successors, Abisare (c. 1905) and Sumu-el (c. 1894), both took steps to cut Isin completely off from access to canals. After this period, Isin quickly lost political and economical force.

arsa grew powerful, but it never accumulated a huge tract of land. At its peak under king Rim-Sin (c. 1822-1763), Larsa controlled only about 10-15 other city-states, nowhere near the territory controlled by other dynasties in Mesopotamian history. Nevertheless, huge building projects and agricultural undertakings can be validated by archaeological evidence.