He was said to have been the son of Belos or Bel, to have conquered in seventeen years the whole of western Asia with the help of Ariaeus, king of Arabia, and to have founded the first empire.
During the siege of Bactra he met Semiramis, the wife of one of his officers, Onnes, whom he took from her husband and married. The fruit of the marriage was Ninyas, i.e. "The Ninevite."
After the death of Ninus, Semiramis, who was accused of causing it, erected to him a temple-tomb, nine stades high and ten stades broad, near Babylon. According to Castor (ap. Syncell. p. 167) his reign lasted fifty-two years, its commencement falling 2189 BC according to Ctesias.
Another Ninus is described by some authorities as the last king of Nineveh, successor of Sardanapalus.