The rulers of Persia, also known as the Achaemenid Empire, were a series of kings who reigned over ancient Persia from approximately 550 BCE to 330 BCE. The most famous ruler of this empire was Cyrus the Great, who founded the Achaemenid dynasty and expanded the empire to become the largest in the world at that time. The Achaemenid rulers were known for their administrative innovations, such as the use of a standardized currency and a system of satrapies, or provinces, which allowed for efficient governance of their vast territories. The empire eventually fell to the conquests of Alexander the Great in 330 BCE.