Pachomius I (unknown – 1513) was the Ecumenical Patriarch of Constantinople, head of the Eastern Orthodox Church, and ethnarch of all Orthodox Christians living in the Ottoman Empire for a brief time in 1503, and then again from 1504 to his death in 1513.
Early in his reign as Patriarch, Pachomius publicly shamed a deacon named Cyril of Rhodes for actions unbecoming of the Eastern Orthodox faith, and had Cyril exiled and placed under anathema. This disgrace led Cyril to join the Templar Order and use what minimal power he maintained to erode the church's influence from within.
Around 1511, a vengeful Cyril returned to Constantinople and began to plot the Patriarch's murder in retribution for his humiliation. On hearing rumors of Cyril's intentions, the Assassin Mentor Ezio Auditore da Firenze and a trainee Master Assassin confronted and killed the errant deacon after an initial failed attempt, thus eliminating the threat on the Patriarch's life.
- Historically, Pachomius died after being poisoned by one of the monks under his service.