Answer: The Chaldeans were people who lived in southern Babylonia which would be the southern part of Iraq today. Sometimes the term Chaldeans is used to refer to Babylonians in general, but normally it refers to a specific semi-nomadic tribe that lived in the southern part of Babylon. The land of the Chaldeans was the southern portion of Babylon or Mesopotamia. It was generally thought to be an area about 400 miles long and 100 miles wide alongside of the Tigris and Euphrates Rivers.
The Chaldeans are mentioned multiple times in the Bible in both contexts. For example, Genesis 11:28 speaks of Abraham’s father Terah, who was from “Ur of the Chaldeans,” the specific tribe or people known as the Chaldeans. We know from verses such as Genesis 11:31 and Genesis 15:7 that God called Abraham, a Chaldean, out of Ur of the Chaldeans so that Abraham would follow God to the land that God had promised to him and his descendants.
The Chaldeans were an intelligent and sometimes aggressive, warlike people. In 731 BC Ukinzer, a Chaldean, became king of Babylon; however, his reign was short-lived. A few years later Merodach-Baladan, also a Chaldean, became king over Babylon. Then in 626 BC Nabopolassar, another Chaldean, began what would be an extended period of time during which Babylon was ruled by a Chaldean king. During this time the word Chaldean became synonymous for Babylon, and we see many verses in Scripture where the word Chaldean was used to refer to Babylonians in general (Isaiah 13:19; 47:1, 5; 48:14, 20). Successors to Nabopolassar were Nebuchadnezzar, Amel-Marduk, Nabonidus and then Belshazzar, “king of the Chaldeans” (Daniel 5:30).
At the height of the Babylonian Empire, the Chaldeans were an influential and highly educated group of people. Some historians believe that, after Persia conquered Babylon, the term Chaldean was used more often to refer to a social class of highly educated people than to a race of men. The Chaldeans influenced Nebuchadnezzar’s decision to throw Shadrach, Meshach, and Abednego into the fiery furnace (Daniel 3:8) and were well known as wise men and astrologers during the time of Jewish captivity in Babylon. (Daniel 1:4; 2:10; 4:7; 5:7, 11). At the time of Daniel, Babylon was the intellectual center of western Asia, and the Chaldeans were renowned for their study and knowledge of astrology and astronomy. They kept detailed astronomical records for over 360 years, which can help us understand how the wise men from the East would have been able to recognize and follow the star that would lead them to the King of the Jews (Matthew 2:2).