- 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
- Judges--Selection and appointment1
- Judgment of God1
- Julii family1
- Justice, Administration of1
- Kingdom of God1
- Kings and rulers--Succession1
- Kloster Medingen1
- Knowledge, Theory of (Religion)1
- Kölner Dom1
- Labyrinths1
- Lafões, Pedro Henrique de Bragança, Duque de, 1718-17611
- Land tenure--Law and legislation1
- Land titles--Registration and transfer1