Author
- John of Lancaster, 1st Duke of Bedford1
- John, Duke of Berry1
- Josephus1
- José Antonio de Alzate y Ramírez1
- João Freire1
- João Gomes da Silva1
- Juan Félix de Rújula1
- Juan Gallo1
- Juan Ortiz Campoy1
- Juan de Mena1
- Juan de Torquemada1
- Juan de Zumárraga1
- Judah Leib Ben Zeev1
- Julius III1
- Jñānamṛtapata1
- Kalonymus ben Kalonymus1
- Kamal Khujandi1
- Kamal al-Din ibn al-Humam1
- Kamalakara1
- Kamāl al-Dīn Turkumānī1