Christianity in Iran has a long history, dating back to the early years of the faith. It is older than the State Religion, Islam itself. It has always been a minority religion, with the majority state religions Zoroastrianism before the Islamic conquest, Sunni Islam in the Middle Ages and Shia Islam in modern times though it had a much larger representation in the past than it does today.
Iranian-Armenians, are Iranian citizens who are ethnically Armenian. They are mostly concentrated in Tehran, Tabriz and Jolfa district, Isfahan, and an estimated 150,000 - 300,000 currently reside in Iran. The Iranian-Armenians were very influential and active in the modernization of Iran during the 19th and 20th centuries. After the Iranian Revolution, many Armenians emigrated to Armenian diasporic communities in North America and Western Europe. Today the Armenians are Iran's largest Christian religious minority.
Iranian Assyrians, are an ethnoreligious and linguistic minority in present-day Iran. The Assyrians of Iran are Eastern Rite Christians belonging mostly to the Assyrian Church of the East and, to a lesser extent, to the Chaldean Catholic Church. They share a common identity, rooted in shared linguistic and religious traditions, with Assyrians in Iraq and elsewhere in the Middle East, as well as with the Assyrian diaspora. The Assyrian community in Iran numbered approximately 200,000 prior to the Islamic Revolution of 1979, after the revolution many Assyrians left the country, primarily for the United States. the Assyrian population in Iran range from 32,000 (as of 2005) to 50,000 (as of 2007).The Iranian capital, Tehran, is home to the majority of Iranian Assyrians, approximately 15,000 Assyrians reside in northern Iran, in Orumiyeh and various Assyrian villages in the surrounding area.