Author
- Innocent IV1
- Isaac Israeli ben Joseph1
- Jacob ben Jacob, ha-Kohen, -approximately 12701
- Jacques de Vitry1
- James of Viterbo1
- Johannes de Sacrobosco1
- John XXII1
- John de Breton1
- John de Seccheville1
- Joseph Angelet1
- Joseph ben Abraham Gikatilla1
- Justin1
- Leo Archpriest1
- Leo III1
- Leo X1
- Leon Battista Alberti1
- Leonardo Loredan1
- Leopold Camp1
- Lucan1
- Lucius Annaeus Florus1