Yes he was, one of the most important in fact. As ancient Mesopotamian kings go, his life is one of the best documented. He did fill many of the same roles described in the Bible, but I'll get more into that below.

There were actually two Nebuchadnezzars in Babylonian history. More accurately, there were two kings named Nabû-kudurri-uṣur, which is how it was actually said in their own Akkadian language. Like many names in the Bible "Nebuchadnezzar" is a Latin transliteration of a Hebrew transliteration from the original.

Nebuchadnezzar I was much earlier than his more famous Biblical successor; he reigned in the late 12th century BC and is best known for a war against Elam. In that conflict, he successfully recovered the statue of Marduk from the Esagila, which had been stolen by Elam in an earlier invasion of Babylonia. This was the most important idol, to the most important god, in Babylon's most important temple. As a result it was considered a very important and resulted in monuments and epics being composed at the time.

Fast forward 497 years, to 607 BC, and Nebuchadnezzar II enters the historical record, not as a king, but as a prince, and in the middle of a war at that. His father, King Nabonidus Nabopolassar, had come to power in Babylon in 626 BC, during a time of massive upheaval. For most of the last 300 years, Babylon had been a vassal kingdom dominated by the much larger and more militant Neo-Assyrian Empire, but in 631 Assyria had devolved into civil war. In 627, one claimant came out on top and the wars ended, but Assyria was still weak, and Nabopolassar was able to operate independently and consolidate power in Babylonia.

Then, around 615 BC, he made an alliance with the Medes, another disgruntled former subject of Assyria from northeast Iran, and they invaded Assyria. In 612, the took the Assyrian capital of Nineveh. In 610, Nabopolassar hunted down the last of the remaining Assyrian forces at a city called Harran, and in 607 Nabopolassar returned to Babylon, leaving Nebuchadnezzar in charge of finishing their conquests in the Levant. In 605, Nebuchadnezzar defeated the Egyptian army that had come to assist the Assyrians (and killed the Judahite king Josiah on the way).

Then he made his way south, demanding tribute in Syria, Phoenicia, and Palestine, where he demanded tribute from Judah for the first time. Following standard practice at the time, he would have taken the sons of noble families as hostages, which is the start of the Babylonian Exile depending on how you count. Not long after he had to rush back to Babylon after receiving news of his father's death, at which point he officially became King Nebuchadnezzar II.

Politically, most of his reign was spent consolidating power over territory conquered in the west, including Cilicia in southern Anatolia, Phoenicia (where the city of Tyre was supposedly besieged for 13 years), and in the Levant. This includes the famous Biblical events, where Jerusalem was besieged twice by Nebuchadnezzar with only a small deportation the first time and a much large deportation and destruction of the temple on the second attempt. Both are corroborated by Babylonian evidence. Most of this activity in the west was probably to compete with Egypt, Nebuchadnezzar's only major enemy at this time.

Domestically, Nebuchadnezzar oversaw a slew of new building projects in Babylon, including famous icons like the Ishtar Gate and the Hanging Gardens, which were supposedly built to remind his Median wife, Amytis, of her homeland in the Zagros mountains. Under Nebuchadnezzar, the city occupied more than 2000 acres, which was truly massive for the time.

According to ancient poetry, Nebuchadnezzar's mental health seems to have declined rapidly later in his life, leading him to ignore even his own children and become very suspicious of his sons when he did remember. There's no way to know with certainty, but it certainly sounds like dementia. He died in 562 and the Babylonian throne shifted rapidly first to his son, then to a son-in-law, then a grandson, and then finally to a man named Nabonidus who may or may not have been related by marriage.

So how does this compare to the Bible? Well, for the most part, the Good Book seems to get things right. There's Babylonian written confirmation and archaeological evidence for the two sieges and the deportations. Even if not every Judahite king is mentioned by name outside the Bible, the overall historical picture gives no real reason to dispute the events described.

The part of the Bible where Nebuchadnezzar really falls apart is the Book of Daniel. Daniel is not historically accurate, and historians widely consider the first half of the book to be a collection of folk tales at best, and plain historical fiction at worst. While there were probably exiled Jewish nobles, like Daniel, in Nebuchadnezzar's court, he did not suddenly recognize the Jewish God after failing to execute them. The reason for the blazing furnace, given by Daniel doesn't make sense under Nebuchadnezzar either: he certainly did not build a golden statue of himself and demand that everyone worship him. In fact, Near Eastern kings were almost never considered living gods, and the ones that were lived in the early Bronze Age.

The golden statue in Daniel is, like most of the book a thinly veiled allegory to the later Seleucid king Antiochus IV, whose conflict with Judea is the basis for Hannukah. Daniel was most likely written during the early years of the Maccabean Revolt, and contains many allusions and allegorical critiques of the Seleucids framed in the guise of earlier Near Eastern kings.

In the same vein, Daniel portrays Belshazzar as the son and successor of Nebuchadnezzar. This is incorrect. Belshazzar was the son of Nabonidus and never became king himself, though he effectively ruled Babylonia for 10 years while his father was away - a controversial excursion that could be it's own post. The historical portion of the book of Daniel continues on with similar inaccuracies.