Dayro d-Mor Mattai (The Monastery of St. Matthew) is a Syriac Orthodox Church monastery on Mount Alfaf in northern Iraq, 20 kilometers northeast of the city of Mosul. It is recognized as one of the oldest Christian monasteries in existence.
The monastery was famous for the number of monks and scholars it housed, and for its large library and considerable collection of Syriac Christian manuscripts. Today, it is an archbishopric; the current Archbishop is Mor Timothius Mousa Alshamany.