Babylonia was an ancient Akkadian-speaking state and cultural area based in central-southern Mesopotamia (present-day Iraq). A small Amorite-ruled state emerged in 1894 BC, which contained the minor administrative town of Babylon. It was merely a small provincial town during the Akkadian Empire (2335–2154 BC) but greatly expanded during the reign of Hammurabi in the first half of the 18th century BC and became a major capital city. During the reign of Hammurabi and afterwards, Babylonia was called "the country of Akkad" (Mat Akkadi in Akkadian).
From c. 3500 BC until the rise of the Akkadian Empire in the 24th century BC, Mesopotamia had been dominated by largely Sumerian cities and city states, such as Ur, Lagash, Uruk, Kish, Isin, Larsa, Adab, Eridu, Gasur, Assur, Hamazi, Akshak, Arbela and Umma, although Semitic Akkadian names began to appear on the king lists of some of these states (such as Eshnunna and Assyria) between the 29th and 25th centuries BC. Traditionally, the major religious center of all Mesopotamia was the city of Nippur where the god Enlil was supreme, and it would remain so until replaced by Babylon during the reign of Hammurabi in the mid-18th century BC.
Southern Mesopotamia had no natural, defensible boundaries, making it vulnerable to attack. After the death of Hammurabi, his empire began to disintegrate rapidly. Under his successor Samsu-iluna (1749–1712 BC) the far south of Mesopotamia was lost to a native Akkadian-speaking king Ilum-ma-ili who ejected the Amorite-ruled Babylonians. The south became the native Sealand Dynasty, remaining free of Babylon for the next 272 years.
Babylonia remained in a state of chaos as the 10th century BC drew to a close. A further migration of nomads from the Levant occurred in the early 9th century BC with the arrival of the Chaldeans, another nomadic northwest Semitic people described in Assyrian annals as the "Kaldu". The Chaldeans settled in the far southeast of Babylonia, joining the already long extant Arameans and Suteans. By 850 BC the migrant Chaldeans had established their own land in the extreme south east of Mesopotamia.
Bronze Age to Early Iron Age Mesopotamian culture is sometimes summarized as "Assyro-Babylonian", because of the close ethnic, linguistic and cultural interdependence of the two political centers. The term "Babylonia", especially in writings from around the early 20th century, was formerly used to also include Southern Mesopotamia's earliest pre-Babylonian history, and not only in reference to the later city-state of Babylon proper. This geographic usage of the name "Babylonia' has generally been replaced by the more accurate term Sumer or Sumero-Akkadian in more recent writing, referring to the pre-Assyro-Babylonian Mesopotamian civilization.