Dayro d-Mor Hananyo was founded in 493 by Mor Shlemon on the site of a sun worship tempel of the Assyrian god Shamash that was converted into a citadel by the Romans. After the Romans withdrew from the fortress, Mor Shlemon transformed it into a monastery. In 793 the monastery was renovated after a period of decline, by the Bishop of Mardin and Kfartuta, Mor Hananyo, who gave the monastery its current name.
The monastery was later abandoned and re-founded by the bishop of Mardin, John, who carried out important renovations before he died at the monastery on the 12th of July 1165. From 1160 until 1932 it was the official seat of the patriarch of the Syriac Orthodox Church, afterwards it was moved to Damascus.
The monastery has 365 rooms - one for each day of the year.