John Dailam (or Deylam) (Yohannan Daylamáyá) (born in 660 and died 26 January 738) is a saint of the Assyrian Church of the East and Syriac churches. He was a monk who founded several monasteries in Mesopotamia and Persia after the Muslim conquest.
His Syriac hagiography says he was born in Ḥdattā village at the confluence of the Great Zab and Tigris, in the year 660AD. He entered the Bet'Ābē monastery at a very young age. Later, he was taken prisoner by Daïlamites, (Iranian tribe) in their war against the Arab invaders, and deported to the Daylam mountains, near the Caspian Sea. He was finally released and seeks to evangelize Daïlamites.
The hagiography also describes the healing of the daughter of an Umayyad Caliph thanks to John. Under the protection of the Caliph Abd al-Malik ibn Marwan (685-705), and Al-Hajjaj ben Yusef the Umayyad governor, John travel to Behbahan in Fārs (in present Khuzestan in southwestern Iran) where, through a property tax exemption obtained by the Caliphs gratitude, he founded at least two monasteries, one whose liturgical language is Persian and the other Kaskar, Syriac. There he died in 738.
It is also mentioned in various manuscripts of his journey to Bakhdida in Mesopotamia, where he founded a monastery that bears his name. However, some historiens think it had been founded by the Nestorians and was returned to Orthodoxy by John.