Author
- John Versor1
- John Wycliffe1
- John XXI1
- John Zonaras1
- John of Damascus1
- John of Garland1
- John of Howden1
- John of Seville ?1
- Joseph Haslewood1
- Joseph ben Moses Sarfati1
- Josephus1
- Judah ben Saul ibn Tibbon1
- Julianus Pomerius1
- Jullien Gervais1
- Junayd ibn Sandal Baghdādī1
- Justin1
- Justinian I1
- Jörg Muelich1
- Kamal Khujandi1
- Kamal al-Din ibn al-Humam1