Which dynasty made Zoroastrianism the state religion of Persia?

The Sassanid dynasty made Zoroastrianism the state religion of Persia.

The dynasty, more commonly spelled Sasanian in modern scholarship, began when Ardashir I defeated the last Parthian ruler in 224 CE. The new monarchy used Zoroastrian belief and priestly institutions to strengthen royal authority and unify a politically fragmented Iranian world.

Zoroastrianism had existed in Persia long before the Sasanians, including under the Achaemenids and Parthians. However, the Sasanians promoted a more centralized religious order, supported the Zoroastrian priesthood, organized sacred fires, and encouraged the collection and interpretation of religious texts. Their capital was Ctesiphon, and the empire lasted until the Arab-Muslim conquest in the seventh century.

A common mix-up is choosing the Achaemenids because they ruled the famous earlier Persian Empire. The Achaemenids clearly followed Iranian religious traditions, but the Sasanians are the dynasty specifically associated with establishing Zoroastrianism as the empire’s official state religion. The Parthians preceded them, while the Seleucids were a Hellenistic dynasty founded after Alexander’s conquests.