Author
- Henry of Langenstein2
- Henry of Segusio2
- Immanuel Bonfils2
- Innocent V2
- Jacob Anatoli2
- Jacobus de Cessolis2
- Jacques Legrand2
- James of Milan2
- Jean de Meun2
- Joan Martines2
- Joannes Oliva2
- Johannes de Sacrobosco2
- John Burgh2
- John Felton2
- John of Genoa2
- John of Wales2
- Juana I of Castile2
- Julian of Toledo2
- Justin2
- Laurent d'Orleans2