Symeon I of Trebizond
Symeon I of Trebizond was Patriarch of Constantinople in 1466, then from 1471 to 1474, and finally again from 1481 to 1486.
Symeon’s early life is unknown, other than he was a monk from Trabizond.
After Marcus II Xylokaraves was installed as patriarch in 1466, a faction of Christians from Trebizond approached the Ottoman Sultan Mechmet II with a monetary offer for his support in an opposition to Marcus, whom they proposed to remove from office in favor of Symeon from Trebizond. Although initially finding the offer comical, the Sultan considered the greed, stupidity, and ungodly manners of his Christian subjects and saw an opportunity for starting a policy of requiring monetary payments for installing new patriarchs to the throne of Constantinople as a regular custom.
After agreeing to support their false charge of simony, the Sultan sent the conspirators to elect a new patriarch. With a charge of simony, Marcus was tried before a synod, condemned, deposed, and anathematized. Symeon was then duly elected, consecrated, and installed as patriarch. A few months later, the step-mother of the sultan, a Christian, sponsored a friend of hers, Dionysius of Philippolis, for the patriarchal throne. With the receipt of tribute money from his step-mother, the Sultan ordered deposition of Symeon.
After his disposition Symeon retired to a monastery until 1471 when he was recalled by the synod after Dionysius resigned in disgust after defending himself successfully from a false charge of apostasy. After the now expected payment of the fee for confirmation of his election, Symeon returned to the Patriarchal throne. Three years later, however, Symeon was confronted by the ambitious Serbian monk, Raphael, who obtained the dethronement of Symeon by changing the investiture fee to an annual tribute. 
Symeon retired to a monastery near Stenimachos for the next seven years before he was once again re-called to the patriarchal throne in 1481. He remained patriarch until 1486. During this term as patriarch he convened a council that condemned the Council of Florence. He was succeeded in 1486 by Nephon II. The date of his repose is unknown.
- Claude Delaval Cobham, The Patriarchs of Constantinople, H.T. E. Duckworth, Introduction II, 75-77