The Sasanian dynasty was founded in 224 CE when Ardashir I overthrew the Parthians. The new state explicitly claimed the legacy of the Achaemenid Persian Empire: it revived Zoroastrianism as a state religion, established Middle Persian (Pahlavi) as the administrative standard, and built a centralized bureaucracy.

For four centuries, the Sasanians coexisted as the great-power rival of Rome and then Byzantium. Their territory stretched from the Euphrates to the Indus. Border wars were frequent but rarely decisive; neither power could eliminate the other.

The Sasanian court was among the most brilliant cultural centres of Late Antiquity. Architecture (the colossal arch of Taq Kasra), science (the Gondishapur academy of medicine and philosophy), literature, and the visual arts all flourished. A large part of the Jewish Talmud was compiled in Sasanian Mesopotamia.

The empire dissolved in the 7th-century Muslim conquests — yet Sasanian administrative models, art, and many cultural forms were inherited by the Abbasid Caliphate and shaped subsequent Iranian history.