Gregory III of Constantinople
| Gregory III of Constantinople | |
|---|---|
| Ecumenical Patriarch of Constantinople | |
| Church | Church of Constantinople | 
| In office | Summer 1445 – Summer 1450 | 
| Predecessor | Metrophanes II of Constantinople | 
| Successor | Athanasius II of Constantinople | 
| Personal details | |
| Born | Before c. 1420 | 
| Died | 1459 Rome, Papal States | 
| Denomination | Eastern Catholic Churches Eastern Orthodox Church (Before 1449) | 
| Sainthood | |
| Venerated in | Catholic Church | 
| Title as Saint | Wonderworker | 
| Canonized | 1459 Papal State by Pius II | 
| Patronage | Catholic-Eastern Orthodox Reunification | 
Gregory III of Constantinople, (surnamed Mammis or Μammas, Greek: Γρηγόριος Μαμμῆς; before c. 1420 – 1459), was Ecumenical Patriarch of Constantinople within the Church of Constantinople during the period 1445–1450. He was prominent in unsuccessful initiatives toward reunification with the Catholic Church.