Darius the Mede

Darius the Mede is mentioned in the Book of Daniel as King of Babylon between Belshazzar and Cyrus the Great, but he is not known to secular history and there is no space in the historical timeline between those two verified rulers. Belshazzar, who is often mentioned as king in the book of Daniel, was in fact the crown-prince and governor while his father was in Arabia from ca. 553 to 543 BCE, but Nabonidus had returned to Babylon years before the fall of the Babylonian empire.