Author
- John II of Castile1
- John Lydgate1
- John Versor1
- John XXI1
- John Zonaras1
- John of Garland1
- John of Seville ?1
- Joseph Haslewood1
- Joseph ben Moses Sarfati1
- Josephus1
- Juan de Torquemada1
- Juana I of Castile1
- Julianus Pomerius1
- Kalonymus ben Kalonymus1
- Kamal al-Din ibn al-Humam1
- Khvājah Muḥammad Pārsā1
- Konrad III. von Soltau1
- Laurentius Cynthius1
- Leo I1
- Leon Battista Alberti1