Author
- John Cornelius1
- John Frederick II of Saxony1
- John II of Castile1
- John of Ibelin1
- Joseph ben Gorion1
- Josephus1
- Joshua Benzion Segre1
- Juan Gallo1
- Juan Valenzuela Velázquez1
- Juan Vicente de Güemes, 2nd Count of Revillagigedo1
- Juan de Foxá1
- Juan de Mena1
- Juan de Mongaston1
- Juan de Torquemada1
- Judah Leib Ben Zeev1
- Judah ben Saul ibn Tibbon1
- Jñānamṛtapata1
- Kalim Kashani1
- Kamal Khujandi1
- Kamal al-Din ibn al-Humam1