- Jiménez de Enciso, Diego1
- Jiménez de Enciso, Pedro1
- Jiří, z Poděbrad, King of Bohemia, 1420-14711
- Joachim, Saint1
- Joannes de Caligariis1
- Job (Biblical figure)1
- Johannes filius Roberti de Cruce1
- John II, King of Aragon, 1397-14791
- John II, King of Portugal, 1455-14951
- John IV, King of Portugal, 1604-16561
- John Manuel, Prince of Portugal, 1537-15541
- John V, King of Portugal, 1689-17501
- John VIII Palaeologus, Emperor of the East, 1392-14481
- John the Baptist's Day1
- John, Duke of Burgundy, 1371-14191
- John, King of England, 1167-12161
- John, of Damascus, Saint1
- John, of Daylam1
- Jonah (Biblical prophet)1
- Juan II, King of Castile and Leon, 1405-14541