The Achaemenid Empire or Achaemenian Empire[16] (/əˈkiːmənɪd/; Old Persian: 𐎧𐏁𐏂, Xšāça, lit. 'The Empire'[17] or 'The Kingdom'[18]) was the ancient Iranian empire founded by Cyrus the Great in 550 BC, known also as the First Persian Empire.[19] Based in Western Asia, it was the largest empire the world had ever seen at its time, spanning a total of 5.5 million square kilometres (2.1 million square miles) from the Balkans and Egypt in the west to Central Asia and the Indus Valley in the east.[12][13]