Author
- John of Lancaster, 1st Duke of Bedford1
- John of Seville ?1
- John of Wales1
- John, Duke of Berry1
- Joseph Haslewood1
- 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
- Jörg Muelich1
- Kalonymus ben Kalonymus1
- Kamāl al-Dīn Turkumānī1
- Kingdom of England1
- Kingdom of Naples1
- Klaus von Stille1
- Konrad III. von Soltau1