| John VIII Palaiologos | |
|---|---|
| Emperor and Autocrat of the Romans | |
 Detail from The Middle King by Benozzo Gozzoli, in the Magi Chapel of Palazzo Medici-Riccardi, Florence, 1459–1461. It is widely believed to represent John VIII. | |
| Byzantine emperor | |
| Reign | 21 July 1425 – 31 October 1448 |
| Coronation | 19 January 1421 |
| Predecessor | Manuel II Palaiologos |
| Successor | Constantine XI Palaiologos |
| Proclamation | c. 1407 as co-emperor |
| Born | 18 December 1392 |
| Died | 31 October 1448 (aged 55) |
| Spouse | |
| Dynasty | Palaiologos |
| Father | Manuel II Palaiologos |
| Mother | Helena Dragaš |
| Religion | Eastern Catholic Previously Eastern Orthodox |
John VIII Palaiologos or Palaeologus (Greek: Ἰωάννης Παλαιολόγος, romanized: Iōánnēs Palaiológos; 18 December 1392 – 31 October 1448) was the penultimate Byzantine emperor. Ruling from 1425 to 1448, he attempted to bring about the reunification of the Orthodox and Catholic churches and prioritized the protection of Constantinople against the Ottoman Empire. He was succeeded by his brother, Constantine XI.