The Achaemenid Persian Empire emerged in the mid-6th century BCE when Cyrus II (reign 559–530 BCE) united the Persian tribes and overthrew the Median kingdom (circa 550 BCE), establishing a new imperial state that would reshape the political landscape of the Ancient Near East. Under Cyrus and his successors, the empire expanded rapidly across Anatolia, Mesopotamia, and the eastern Iranian plateau. By the early 5th century BCE, during the reign of Darius I (reign 522–486 BCE), the Achaemenid realm reached its greatest extent, integrating the three great early centers of civilization: Mesopotamia, the Nile Valley, and the Indus River valley. This unified territory became a vast administrative and cultural network linking peoples, religions, and economies across more than 5,000 km.

For nearly two centuries, the Achaemenid Empire functioned as a sophisticated imperial system characterized by satrapal governance, standardized taxation, an extensive road network, monumental architecture, and a policy of cultural accommodation that allowed diverse communities to maintain local traditions. Its cities, Persepolis, Susa, Babylon, Memphis, served as hubs of diplomacy, scholarship, and artistic production, illustrating the empire’s role as a center of innovation in science, engineering, religion, and statecraft. The empire’s decline began in the 4th century BCE amid internal revolts and external pressures, culminating in its conquest by Alexander III, the Great, of Macedon (reign 336–323 BCE) in 329 BCE. Yet its administrative models, artistic traditions, and political ideals profoundly influenced later empires across the Mediterranean and the Near East.