Author
- Jewish Community of Pitigliano, Italy1
- Jewish community of unidentified city, Italy1
- Joannes de Crivelli1
- John Dominici1
- John XXI1
- John XXII1
- John de Breton1
- John de Seccheville1
- Joseph Trani1
- Joseph ben Abraham Gikatilla1
- Josephus1
- Joshua Benzion Segre1
- Julianus Pomerius1
- Justin1
- Lapo da Castiglionchio1
- Laurentius Cynthius1
- Leo Archpriest1
- Leo I1
- Leo III1
- Leo X1