- John IV, King of Portugal, 1604-16561
- John Manuel, Prince of Portugal, 1537-15541
- John V, King of Portugal, 1689-17501
- John the Baptist's Day1
- John, Duke of Burgundy, 1371-14191
- John, King of England, 1167-12161
- Jonah (Biblical prophet)1
- Joseph (Son of Jacob)1
- Juana, of Austria, Princess of Portugal, 1535-15733
- Judaism1
- Judaism--Customs and practices2
- Judaism--Liturgy2
- Judaism--Liturgy--Texts1
- Judgment of God2
- Jugurthine War (111-105 B.C.)1
- Julian, of Eclanum, Bishop, 380-approximately 4551
- Justa, Saint, -approximately 2871
- Justinian I, Emperor of the East, 483?-5651
- Karo-Batak dialect1
- Kekchi language1