On May 7 (20) the Georgian Orthodox Church marks the commemoration day of Thirteen Assyrian Fathers.

The Thirteen Assyrian Fathers were, according to Georgian church tradition, a group of monastic missionaries who arrived from Mesopotamia to Georgia to strengthen Christianity in the country in the 6th century. They are credited by the Georgian church historians with the foundation of several monasteries and hermitages and initiation of the ascetic movement in Georgia.

The lives of the Assyrian Fathers are related in a cycle of medieval Georgian hagiographic texts and are unattested beyond these sources. Some of these vitae are formalities composed for an 18th-century synaxary, but four of them exist in original form, as well a metaphrastic versions. The dating as well as authorship of these texts is controversial. The Georgian Catholicoi Arsen I (830-87) and Arsen II (955-80) have been suggested as authors of some of the vitae. Other, unattributed, texts may have been composed earlier, in the late 7th century.

Many monasteries in modern Georgia are named after the Assyrian Fathers and are said to have been founded and led by them and their numerous disciples. In the Middle Ages, these religious foundations played an important role in forging Georgian Christian identity.

Tradition, written and oral, names as many as 19 Assyrian monks active in Georgia in the 6th century and the number "13" seems to be largely symbolic. Modern scholarly opinion is divided as to whether they were Assyrians Assyrian-educated Georgians, whether missionaries or refugees — monophysite or diophysite — from Syria, from which monophysitism had retreated while Georgia was still primarily monophysite at that time.

Chief of the Assyrian Fathers were:

Davit Garejeli (დავით გარეჯელი) / David of Gareja

Ioane Zedazneli (იოანე ზედაზნელი) / John of Zedazeni

Abibos Nekreseli (აბიბოს ნეკრესელი) / Abibos of Nekresi

Shio Mgvimeli (შიო მღვიმელი) / Shio of Mgvime

Ioseb Alaverdeli (იოსებ ალავერდელი) / Joseph of Alaverdi

Anton Martqopeli (ანტონ მარტყოფელი) / Anton of Martqopi

Tadeoz Stepantsmindeli (თადეოზ სტეფანწმინდელი) / Thaddeus of Stepantsminda

Piros Breteli (პიროს ბრეთელი) / Pyrrhus of Breti

Ise Tsilkneli (ისე წილკნელი) / Jesse of Tsilkani

Stepane Khirseli (სტეფანე ხირსელი) / Stephen of Khirsa

Isidore Samtavneli (ისიდორე სამთავნელი) / Isidor of Samtavisi

Mikael Ulumboeli (მიქაელ ულუმბოელი) / Michael of Ulumbo

Zenon Iqaltoeli (ზენონ იყალთოელი) / Zeno of Iqalto