Nabonidus, king of Babylonia from 556 until 539 bc, when Babylon fell to Cyrus, king of Persia. After a popular rising led by the priests of Marduk, chief god of the city, Nabonidus, who favoured the moon god Sin, made his son Belshazzar coregent and spent much of his reign in Arabia. Returning to Babylon in 539 bc, he was captured by Cyrus’ general Gobryas and exiled.