Aba I

Mar Abba the Great
Mar Abba the Great, Patriarch of Seleucia-Ctesiphon
Catholicos Patriarch
Born	Hala, Asorestan, Sasanid Iran
Died	552 Adurbadagan, Sasanid Iran
Venerated in	Assyrian Church of the East Ancient Church of the East Chaldean Catholic Church Roman Catholic Church
Major shrine	The Seminary of Mar Abba the Great El Cajon, California, United States
Feast	28 February

Aba I (or, with his Syriac honorific, Mar Aba I) or Mar Abba the Great was the Patriarch of the Church of the East at Seleucia-Ctesiphon from 540 to 552. He introduced to the church the anaphoras of Theodore of Mopsuestia and Nestorius beside the more ancient liturgical rite of Addai and Mari. Though his tenure as catholicos saw Christians in the region threatened during the Persian-Roman wars and attempts by both Sassanid Persian and Byzantine rulers to interfere with the governance of the church, his reign is reckoned a period of consolidation, and a synod he held in 544 as (despite excluding the Diocese of Merv) instrumental in unifying and strengthening the church. He is thought to have written and translated a number of religious works. After his death in February 552, the faithful carried his casket from his simple home across the Tigris to the monastery of Mar Pithyon.

Aba is a highly regarded and significantly venerated saint in the Assyrian Church of the East, the Ancient Church of the East, and the Chaldean Catholic Church, which has a seminary in San Diego, California, USA, is named after him. His feast day is celebrated on both the seventh Friday after Epiphany and on February 28.

He is documented in the Ausgewählte Akten Persischer Märtyrer, and The Lesser Eastern Churches, two biographies of Eastern saints.

Born in a Zoroastrian family of Persian origin in Hala, Mesopotamia. Mar Aba was secretary to the governor of Beth Garmai province before he converted to Christianity, studied, and later taught at the School of Nisibis. Highly regarded as a scholar, he studied Greek in Edessa and is attributed with the translation (or with having overseen the translation) of key texts, including the works of Theodore and Nestorius, from Greek into Syriac. He is also remembered as the author of original works including Biblical commentaries, homilies, and synodal letters.