Author
- John Tiptoft, 1st Earl of Worcester1
- John Versor1
- John Wycliffe1
- John XXI1
- John of Glastonbury1
- John of Howden1
- John of Seville ?1
- Juan de Torquemada1
- Julianus Pomerius1
- Justin1
- Justinian I1
- Jörg Muelich1
- Kingdom of England1
- Kingdom of Naples1
- Konrad III. von Soltau1
- Lambert le Bègue1
- Laurentius Cynthius1
- Leo Archpriest1
- Leopold Camp1
- Lope de Espejo1