Iran did not become “Islamic” in a single moment; it went through two big turning points: first, a long conversion to Islam after the Arab-Muslim conquest in the 600s–1000s, and much later the creation of the modern Islamic Republic in 1979.

Quick Scoop

  • The Islamization of Iran began after the Arab-Muslim conquest of the Sasanian Empire in the 7th century, around 633–651 CE.
  • Most people in Iran had become Muslim by roughly the 10th–11th centuries , after several generations of gradual conversion.
  • Iran was mostly Sunni for many centuries and then was forcibly turned majority Shia by the Safavid dynasty starting around 1500 CE.
  • The state we know today as the Islamic Republic of Iran was officially proclaimed on April 1, 1979 , after a national referendum following the Iranian (Islamic) Revolution.

So, depending on what is meant by “when did Iran become Islamic”:

  • As a majority Muslim society : roughly by the 10th–11th century.
  • As a Shia-majority realm : early 1500s under the Safavids.
  • As the modern Islamic Republic : April 1, 1979.

Information gathered from public forums or data available on the internet and portrayed here.