The country between the Caspian Sea and Elam, bounded by Mount Zagros on the west and Parthia on the east. It was at one time a tributary province of the Assyrian Empire, but shook off the yoke in the reign of Assurbanipal (666–624 B.C.), and the Median king Cyaxares joined with the Babylonian king Nabopolassar in the overthrow of Nineveh. Cyrus, by his defeat of Astyages (550 B.C.), gained possession of Media, which he united with the Persian kingdom.