Author
- John of Seville ?1
- John, Duke of Berry1
- Joseph Angelet1
- Joseph Haslewood1
- Joseph ben Abraham Gikatilla1
- Joseph ben Moses Sarfati1
- Juan de Torquemada1
- Juana I of Castile1
- Judah ben Saul ibn Tibbon1
- Julianus Pomerius1
- Jullien Gervais1
- Junayd ibn Sandal Baghdādī1
- Justin1
- Justinian I1
- Jörg Muelich1
- Kalonymus ben Kalonymus1
- Kamal Khujandi1
- Khayr al-Dīn Khalīl1
- Khvājah Muḥammad Pārsā1
- Khālid ibn ʻAbd Allāh al-Azharī1