Hierarch Eugene I of Rome (Orthodox veneration unconfirmed)

Eugene I was elected Pope of Rome in 654 after the Byzantine authorities forcibly deposed and exiled Pope Martin I to Cherson (June 18, 653) for his condemnation of Monothelitism — the doctrine of a single will in Christ — at the Lateran Council of 649, a direct challenge to Emperor Constans II's Typos edict. Eugene was elected with the tacit consent of the Byzantine exarch and, unlike Martin, sought to avoid open confrontation with imperial authority. Nonetheless he maintained his predecessor's doctrinal (anti-Monothelite) position and refused eucharistic communion with the Monothelite-leaning Patriarch Peter of Constantinople; tradition holds that Roman clergy and laity would not allow him to celebrate the liturgy until he publicly rejected Peter's compromise proposals. The controversy was only finally resolved after Eugene's death, at the Sixth Ecumenical Council (Constantinople, 680-681), which condemned Monothelitism. Eugene died on June 2, 657, in Rome.

IMPORTANT CAVEAT: the Orthodox Encyclopedia itself (pravenc.ru) explicitly states that Eugene I's name "does not appear in any ancient Martyrology or calendar; there is no record of his veneration in Rome" — the June 2 commemoration was added to the Roman Martyrology many centuries later by the Catholic Cardinal Caesar Baronius. A check of the complete Orthodox calendar for June 2 (N.S.) confirmed that Pope Eugene I's name does not appear on that date (commemorated instead are St. Nicephorus of Constantinople, Great Martyr John the New of Suceava, the Martyrs of Lyons, and Righteous Juliana of Vyazma). Thus Eugene I is a genuine historical figure, but his veneration as a saint is reliably attested only in the Western (Catholic) tradition; for the Orthodox calendar this entry is unconfirmed and should be handled with caution.