Author
- Joannes Dominicus de Marchis1
- Joannes Thomas Beltamino1
- Johannes Cnipius1
- Johannes Mellarinus1
- Johannes Nider1
- Johannes Tostius1
- Johannes von Kastl1
- Johannis Hieronymus1
- John Burgh1
- John Cornelius1
- John Felton1
- John Mandeville1
- John Versor1
- John XXI1
- Juan Valenzuela Velázquez1
- Juan de Torquemada1
- Justinian I1
- Kingdom of England1
- Kingdom of Naples1
- Konrad III. von Soltau1