Theoktistos Vriennion (Greek: Θεόκτιστος), (d. November 20, 855), was a Logothetes, a powerful Byzantine official, responsible for the diplomatic relations of the Empire and a promoter of major educational programs within the Empire. He had proved time and again to be a very competent and very faithful servant to the Empire. He served Michael II, Theophilos' father, and Theophilus, who had appointed him to the regency council for his son Michael III and Empress Theodora. After the death of Theophilus (820-842), a regency was set up consisting of Theoktistos, Empress Theodora, and the Empress' brothers, Bardas and Petronas.

Theoktistos Vriennion also was the uncle of Cyril and Methodius. In 843 he invited Cyril and Methodius in Constantinople to help with their studies and arrange the placement of Methodius as a commander of a Slavic administrative region.

On 849 the war campaigns of the Empire were unsuccessful and Logothetis Theoktistos failed to recapture Crete from the Saracens who continued their raids into the empire and extended their conquests in Sicily, although their eastward expansion was temporarily stopped. The Slavic tribes of Moreas revolted against the empire but they were defeated by the protospatharios Theoktistos.

Theoktistos, along with Photios and Bardas, initiated a far- reaching educational program and founded the University of Magnaura. It was during this regency that Leo the Mathematician, Photios who taught Greek Philosophy, and later Constantine-Cyril taught at the university. In the words of Father Dvomik:

"The regime of Theoktistos represents the continuation of the literary and scientific movement which in Byzantium continues from the learned Patriarch John the Grammarian to Leo the Mathematician and from Theophilos to Photios and their school.40"

Recognizing Photios' administrative abilities, he named him Photios protoasecretis around 851, with the rank also of protospatharios. Some scholars believe that the appointment of Photios as protoasecretis was much earlier, probably around 843.

quarrel between the moderates, represented by Gregorios and his followers and friends, and the extremists of the Ignatian party. Gregorios appealed to Rome, and Pope Leo IV sent a letter to Ignatios reprimanding him for his decision.48 There are three contemporary sources for these events, but all are partisans of Ignatios, and thus it is rather difficult to reconstmct the case objectively.49 Nevertheless, the fact is that Ignatios lacked the temperament and diplomatic ability needed to unify the Church; on the contrary, he brought on an internal schism among the clergy.

Meanwhile Bardas and Theoktistos were fighting over who would control the government. Bardas being the uncle of [[Michael III] was elevated to magister and appointed head of the imperial guard. On 855, Michael came of age and turned the control of the government over to his uncle Bardas, raising him to the highest rank-that of caesar. It was then that Bardas and Michael decided to eliminate Theoktistos.