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 kings.[1]
Most scholars view this Darius as a literary fiction, but some have tried to harmonize the Book of Daniel with history by identifying him with various known figures, notably Cyrus, Cyaxares, or Gobryas, the general who was first to enter Babylon when it fell to the Persians in 539 BCE.[2]