Nebuchadnezzar II was the second king of the Chaldean Dynasty in Babylonia, reigning from approximately 605 BC to 561 BC. His father Nabopolassar did not claim to be of royal descent, but Nebuchadnezzar claimed that he was the ancestor of King Naram-Sin and he had personally been granted kingship by the god Marduk.
He is generally known for for conquering Jerusalem, and sending the king of Judah (Jehoiakim) and many of his people to Babylonia. His other conquests include the Scythians and the Cimmerians. He is also credited with breathing new life back into Babylon, building the Median wall, improving the canals, rebuilding the temple of Marduk and constructing the Hanging Gardens of Babylon (which may be mythological, as there are no contemporary accounts of the gardens, and they have left no trace today).
Nebuchadnezzar II is the Nebuchadnezzar of the biblical books of of Daniel, Jeremiah and Ezekiel. His most memorable blbiblical scene probably occurred in Daniel, where he constructed a large idol for public worship, and Meshach, Shadrach, and Abednego are thrown into the fire for refusing to bow before it, only to emerge unharmed*.
For centuries almost all knowledge of Nebuchadnezzar was limited to the bible and the writings of Josephus, however a series of tablets (the Babylonian Chronicle) was found in 1956, and those detail the first 11 years of his reign as king.
*This was easily the favorite story of my sunday school students, however that is probably because they were five years old, and it is a really fun story to act out, getting thrown into the "fire" and all. As often as not King Nebuchadnezzar would end up in the fire right along with Meshach, Shadrach, and Abednego.