Nabopolassar was the first king of the Neo-Babylonian Empire, ruling from November 626 - August 605 B.C. He had been general in a revolt against Assyria after the Assyrian king Assurbanipal died in 631. Nabopolassar was made king on November 23, 626*.
In 614, the Medes, led by Cyaxares (king of the Umman Manda), conquered Assur, and the Babylonians under Nabopolassar joined forces with them. In 612, in the Battle of Ninevah, Nabopolassar of Babylonia, with the assistance of the Medes, destroyed Assyria. The new Babylonian empire incorporated Babylonians, Assyrians, and Chaldeans, and was allies with the Medes. Nabopolasar's empire extended from the Persian Gulf to Egypt.
Nabopolassar restored the temple of the sun god Shamash st Sippar, according to Civilizations of Ancient Iraq.
Nabopolassar was the father of Nebuchadnezzar.
For information on the Babylonian Chronicles which has source material on the Babylonian king, see Livius: Mesopotamian Chronicles.
* The Babylonian Chronicle, by David Noel Freedman The Biblical Archaeologist © 1956 The American Schools of Oriental Research
Also see: A.T. Olmstead's History of the Persian Empire.