Nebuchadnezzar II (Babylonian cuneiform: Nabû-kudurri-uṣur, meaning "Nabu, watch over my heir"; Biblical Hebrew: נְבוּכַדְרֶאצַּר‎ – Nəḇūḵaḏreʾṣṣar or נְבוּכַדְנֶאצַּר‎ – Nəḇūḵaḏneʾṣṣar; Biblical Aramaic: נְבוּכַדְנֶצַּר‎ – Nəḇūḵaḏneṣṣar), also spelled Nebuchadrezzar II, was the second king of the Neo-Babylonian Empire, ruling from the death of his father Nabopolassar in 605 BC to his own death in 562 BC. Historically known as Nebuchadnezzar the Great, he is typically regarded as the empire's greatest king. Nebuchadnezzar remains famous for his military campaigns in the Levant, for his construction projects in his capital, Babylon, and for the important part he played in Jewish history. Ruling for 43 years, Nebuchadnezzar was the longest-reigning king of the Chaldean dynasty. At the time of his death, Nebuchadnezzar was among the most powerful rulers in the world.

Possibly named after his grandfather of the same name, or after Nebuchadnezzar I (r. c. 1125–1104 BC), one of Babylon's greatest ancient warrior-kings, Nebuchadnezzar II already secured renown for himself during his father's reign, leading armies in the Medo-Babylonian war against the Assyrian Empire. At the Battle of Carchemish in 605 BC, Nebuchadnezzar inflicted a crushing defeat on an Egyptian army led by Pharaoh Necho II, and ensured that the Neo-Babylonian Empire would succeed the Neo-Assyrian Empire as the dominant power in the ancient Near East. Shortly after this victory, Nabopolassar died and Nebuchadnezzar became king. Despite his successful military career during his father's reign, the first third or so of Nebuchadnezzar's reign saw little to no major military achievements, and notably a disastrous failure in an attempted invasion of Egypt. These years of lacklustre military performance saw some of Babylon's vassals, particularly in the Levant, beginning to doubt Babylon's power, viewing the Neo-Babylonian Empire as a "paper tiger" rather than a power truly on the level of the Neo-Assyrian Empire. The situation grew so severe that people in Babylonia itself began disobeying the king, some going as far as to revolt against Nebuchadnezzar's rule.

After this disappointing early period as king, Nebuchadnezzar's luck turned. In the 580s BC, Nebuchadnezzar engaged in a successful string of military actions in the Levant against the vassal states in rebellion there, likely with the ultimate intent of curbing Egyptian influence in the region. In 587 BC, Nebuchadnezzar destroyed the Kingdom of Judah, and its capital, Jerusalem. The destruction of Jerusalem led to the Babylonian captivity as the city's population, and people from the surrounding lands, were deported to Babylonia. The Jews thereafter referred to Nebuchadnezzar, the greatest enemy they had faced until that point, as a "destroyer of nations". The biblical Book of Jeremiah paints Nebuchadnezzar as a cruel enemy, but also as God's appointed ruler of the world and a divine instrument to punish disobedience. Through the destruction of Jerusalem, the capture of the rebellious Phoenician city of Tyre, and other campaigns in the Levant, Nebuchadnezzar completed the Neo-Babylonian Empire's transformation into the new great power of the ancient Near East.

In addition to his military campaigns, Nebuchadnezzar is remembered as a great builder king. The prosperity ensured by his wars allowed Nebuchadnezzar to conduct great building projects in Babylon, and elsewhere in Mesopotamia. The modern image of Babylon is largely of the city as it was after Nebuchadnezzar's projects, during which he, among other work, rebuilt many of the city's religious buildings, including the Esagila and Etemenanki, repaired its current palace and constructed a brand new palace, and beautified its ceremonial centre through renovations to the city's Processional Street and the Ishtar Gate. As most of Nebuchadnezzar's inscriptions deal with his building projects, rather than military accomplishments, he was for a time seen by historians mostly as a builder, rather than a warrior.