Chaldea (/kælˈdiːə/) refers to a region probably located in the marshy land of southern Mesopotamia. It is mentioned, with varying meaning, in Neo-Assyrian cuneiform, the Hebrew Bible, and in classical Greek texts. The Hebrew Bible uses the term כשדים (Kaśdim), and this is translated as Chaldaeans in the Christian Greek Old Testament.
During a period of weakness in the East Semitic-speaking kingdom of Babylonia, new tribes of West Semitic-speaking migrants arrived in the region from the Levant between the 11th and 9th centuries BC. The earliest waves consisted of Suteans and Arameans, followed a century or so later by the Kaldu, a group who became known later as the Chaldeans or the Chaldees. These migrations did not affect the powerful kingdom and empire of Assyria in Upper Mesopotamia, which repelled these incursions.