Gregory III of Constantinople | |
|---|---|
| Ecumenical Patriarch of Constantinople | |
| Church | Church of Constantinople |
| In office | 1443–1451 |
| Predecessor | Metrophanes II of Constantinople |
| Successor | Athanasius II of Constantinople |
| Personal details | |
| Born | before c. 1420 |
| Died | 1459 Rome, Papal States |
| Denomination | Eastern Catholicism Eastern Orthodoxy (Before 1449) |
| Sainthood | |
| Venerated in | Catholic Church |
| Title as Saint | Wonderworker |
| Canonized | 1459 Papal State by Pope Nicholas V |
| Patronage | Catholic-Eastern Orthodox Reunification |
Patriarch Gregory III, surnamed Mammis or Μammas (Greek: Γρηγόριος Μαμμῆς; before c. 1420 – 1459), was Ecumenical Patriarch within the Eastern Orthodox Church during the period 1443–1450. He was prominent in unsuccessful initiatives toward reunification with the Catholic Church.