Parthian Empire

The Parthian Empire inherited Persia and Mesopotamia from the Seleucids in 247 BCE, and with them inherited a Zoroastrian tradition that had already survived Alexander's conquest and two centuries of Hellenistic rule without disappearing. A history of Zoroastrianism treats the Parthian period as one of quiet continuity rather than dramatic change: the fire temples and priestly lineages that had served the Achaemenid court persisted under Parthian rule, even as the new dynasty itself, of nomadic Central Asian origin, governed a religiously plural empire that also included Greek cities, Babylonian temple cults, and, in its western territories, Jewish and early Christian communities.

Textual sources for the study of Zoroastrianism from this period are comparatively thin, since much of the Avesta's core material appears to have been transmitted orally through the Parthian centuries before being committed to writing under the Parthians' Sasanian successors, who claimed a more overtly Zoroastrian state ideology than the Parthians had asserted. What survives suggests a Parthian religious landscape more syncretic than either its Achaemenid predecessor or Sasanian successor, absorbing Hellenistic astrological and iconographic conventions into a still recognizably Zoroastrian framework, a hybridity some scholars read as the empire's most distinctive religious contribution.

A study of the Roman cult of Mithras, which appeared across the Roman Empire from the first century CE and became especially popular among soldiers, traces the god's name directly to the Zoroastrian and wider Iranian deity Mithra, and ancient Roman writers themselves sometimes described the mysteries as of Persian origin, transmitted west through territory the Parthian Empire controlled. On this reading, Parthian era Persia would have served as the transmission point through which an ancient Iranian god was carried into an entirely new Roman mystery religion.

That derivation has been argued against by more recent scholarship. A study of the origins of the Mithraic mysteries makes the case that the Roman cult, for all it borrowed the god's name and some Persian sounding imagery, was substantially a Roman invention, its astrological symbolism and initiatory structure owing more to Hellenistic astronomy than to any continuous Persian ritual tradition, with no clear evidence of a Parthian Mithraic mystery cult resembling the Roman one. The dispute remains open rather than settled, and it is a useful example of how thin the Parthian empire's own religious record is: much of what can be said about Parthian era Mithra worship is inferred backward from what the Romans made of the god's name, rather than read directly from Parthian sources.