Patr. 818–45, historian. Dionysios came from the village of Tel Maḥre. He was a monk in the monastery of John bar Aphtonia at Qenneshre, but after its destruction by fire in ca. 810, he moved to another monastery and eventually to the Monastery of Mar Yaʿqub at Kayshum. On 1 Aug. 818 at the synod in Kallinikos, on the suggestion of Bp. Theodoros of the same monastery, Dionysios was elected patr. Then, in three successive days he was ordained deacon, priest, and patriarch (Michael, 503 / III, 43).

At the very beginning of his pontificate he had to face opposition from Abraham, whom Dionysios calls Abiram (cf. Num. 16), a monk of Qarṭmin, and his followers of the Monastery of Gubba Barraya. The group was schismatic (Abraham ordained his own bishops), but also held dissenting views in the matter of the liturgical formula Panem caelestem frangimus (‘We break the heavenly bread’), which they wished to be accepted by the whole Syr. Orth. Church. The conflict in this matter had been troubling the Church already during the pontificate of Dionysios’s predecessor, Patr. Quryaqos. As it proved impossible to solve it, the synod of Kallinikos, at which Dionysios was elected, accepted that the usage of the formula was at the discretion of every bp. However not even this tolerant solution was accepted by Abraham’s group. Dionysios however succeeded in appeasing at least the people and monks of the diocese of Cyrrhus, who previously had supported Abraham. The latter repeatedly presented himself to the Muslim authorities as the legitimate patr., but without receiving official recognition (Michael 507, 508–12 / III, 49, 55–9), due to Dionysios’s intervention. In 820 Dionysios went to Baghdad where he received the confirmation of his election from Caliph al-Maʾmūn. In 829, after long talks with the caliph, Dionysios obtained from him a decree to the effect that non-legitimate bishops would not be officially approved by the Muslims. In this way Abraham no longer presented a threat to Dionysios’s authority or the unity of the Church. He died in 837, but the schism nevertheless continued, as Abraham’s supporters elected his brother Shemʿun counter-patriarch. Some bishops, however, turned their allegiance to Dionysios, so that this later phase of the schism was less troublesome, as Dionysios himself reports (Chronicle of 1234, 234/206).

Another problem Dionysios had to face was the opposition of the eastern (maphrianate) bishops, among whom the main figure was Basil bp. of Tagrit. As he antagonised also the Muslims of his diocese, he was arrested by the Muslim authorities, which however also led to anti-Christian acts of violence, including destruction of churches, e.g., in Edessa and Ḥarran. Dionysios, together with his brother, Theodosios bp. of Edessa, went to Egypt to meet Emir ʿAbdallāh, from whom he received an edict commanding any further destruction of churches to stop and to rebuild the ones that had been destroyed (Michael, 516 / III, 63–4).

Dionysios’s relations with the Muslim authorities were so good that on the caliph’s request he even intervened far beyond his own jurisdiction, namely in the matters of a group of Coptic Christians, known as Bashmurites, who had revolted against their Muslim oppressors. It seems that thanks to his intervention the caliph did not punish them with death but deportation.

During his pontificate Dionysios ordained 99 bishops (Michael, 754–55 / III, 453–55). He died on 22 Aug. 845 and was buried in his former monastery of Qenneshre.

Dionysios was the author of an historical work in two parts, dealing with ecclesiastical (written earlier) and with secular matters, altogether in 16 books. Dedicated to Iwannis of Dara, it covered the period of over two and a half centuries, from the accession of the Byzantine emperor Maurice (582) until the death of Emperor Theophilos and of Caliph Abū Isḥāq al-Muʿtaṣim (842) (Michael, Chronicle, 544 / III, 111). It has not been preserved, except for fragments (ed. Brooks, CSCO 84, 88) and is known mostly from later Syriac chronicles, whose authors used it as their source, namely the anonymous Chronicle of 1234 and the Chronicle of Michael Rabo.

Dionysios’s sources are not directly known, but the analyses by J.-B. Chabot (Introduction to Chronique de Michel, XXXII–XXXIV) and A. Palmer and R. Hoyland (The Seventh Century, 95–104) have identified some of them: Daniel son of Mushe (8th cent.), Yoḥannan son of Shmuʾel, Theophilos the ‘Chalcedonian’, son of Toma of Edessa, the Common Source of the Byzantine chronicler Theophanes (d. 818), the Melkite Agapius of Mabbug, who wrote in Arabic (10th cent.), part of the material preserved in the Chronicle to the year 724, and some other Syriac, but also Greek and Arabic sources.

Due to an erroneous attribution by J. S. Assemani, Dionysios was until the end of the 19th century considered to be the author of the anonymous Chronicle of Zuqnin, which consequently became known as that of Pseudo-Dionysios of Tel Maḥre.

Dionysios also promulgated some disciplinary canons, preserved in the Synodicon of the Syr. Orth. Church (ed. Vööbus). Another text of his is his profession of faith in Arabic, most probably one that he sent to the Coptic patr. of Alexandria (as was customary for newly elected patriarchs of both churches), in which, however, he says nothing about the current issues (the Panem caelestem controversy).