Euthymius I Syncellus was the Ecumenical Patriarch of Constantinople from 907 to 912. A monk since his youth, he became spiritual father of the future emperor Leo VI the Wise, and was raised by him to the high ecclesiastical office of syncellus. Despite his turbulent relationship with Leo, in 907 he was appointed to the patriarchate and held the post until his deposition shortly before or after Leo's death in 912.

Leo VI, also known as Leo the Wise, was Byzantine Emperor from 886 to 912. The second ruler of the Macedonian dynasty, he was very well read, leading to his epithet. During his reign, the renaissance of letters, begun by his predecessor Basil I, continued; but the empire also saw several military defeats in the Balkans against Bulgaria and against the Arabs in Sicily and the Aegean. His reign also witnessed the formal discontinuation of several ancient Roman institutions, such as the separate office of Roman consul.