Ur Kasdim, commonly translated as Ur of the Chaldeans, is a city mentioned in the Hebrew Bible as the birthplace of Abraham, the patriarch of the Israelites and the Ishmaelites. In 1862, Henry Rawlinson identified Ur Kaśdim with Tell el-Muqayyar near Nasiriyah in the Baghdad Eyalet of the Ottoman Empire. In 1927, Leonard Woolley excavated the site and identified it as a Sumerian archaeological site where the Chaldeans were to settle around the 9th century BC. Recent archaeology work has continued to focus on the location in Nasiriyah, where the ancient Ziggurat of Ur is located.

Chaldea was a small country that existed between the late 10th or early 9th and mid-6th centuries BC, after which the country and its people were absorbed and assimilated into the indigenous population of Babylonia. Semitic-speaking, it was located in the marshy land of the far southeastern corner of Mesopotamia and briefly came to rule Babylon. The Hebrew Bible uses the term כשדים (Kaśdim) and this is translated as Chaldaeans in the Greek Old Testament, although there is some dispute as to whether Kasdim in fact means Chaldean or refers to the south Mesopotamian Kaldu.