patriarch of the Syrian Jacobite church and author of an important source document on Eastern Christianity between the reigns of the Byzantine emperors Mauricius (582–602) and Theophilus (829–842).

After some years as a monk in Syria, Dionysius was chosen patriarch and ordained a priest in 818 in the Jacobite church, which took its name from Jacob Baradaeus.

Although Dionysius' position was contested by a rival schismatic group during his entire reign, he succeeded in effectively governing the Syrian community. Through cordial relations with the Muslim rulers, Dionysius prevented violent suppression of the Syrian Christians and wholesale sacking of their property. The persecution, however, resumed toward the end of his life.

Dionysius' chronicles, although uncritical and only partly preserved in manuscript, retain their value as source data on life in the premedieval Syrian church. They were included in subsequent Syriac annals and contributed a distinctive stage in the development of its literary culture.