- 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
- Jonah (Biblical prophet)1
- Juana, of Austria, Princess of Portugal, 1535-15731
- Judaism (Christian theology)1
- Judaism--Liturgy1
- Judas Iscariot1
- Judges1
- Judges--Selection and appointment1
- Judgment of God1
- Julii family1
- Julius III, Pope, 1487-15551
- Justice, Administration of1
- János I Zápolya, King of Hungary, 1487-15401
- Kapitalbünde1
- Kings and rulers--Succession1
- Kirchmair, Georg, 1481-15541
- Kloster Medingen1