King of Kings was a ruling title employed primarily by monarchs based in the Middle East. Although most commonly associated with Iran, especially the Achaemenid and Sasanian Empires, the title was originally introduced during the Middle Assyrian Empire by king Tukulti-Ninurta I and was subsequently used in a number of different kingdoms and empires, including the aforementioned Persia, various Hellenic kingdoms, India, Armenia, Georgia, and Ethiopia.

The history of Iran is intertwined with that of Greater Iran, a sociocultural region spanning the area between Anatolia in the west and the Indus River and Syr Darya in the east, and between the Caucasus and Eurasian Steppe in the north and the Persian Gulf and the Gulf of Oman in the south. Central to this area is the modern-day country of Iran, which covers the bulk of the Iranian plateau.