Author
- John Halgren of Abbeville2
- John Montgomery2
- John Wycliffe2
- John XXII2
- John de Beauchesne2
- John of Garland2
- John of Genoa2
- Jordan von Quedlinburg2
- Josef ibn Tabul2
- Joseph ben Gorion2
- Judah Leib Pukhovitser2
- Judah Rosanes2
- Julian of Toledo2
- Julianus Pomerius2
- Julius II2
- Justin2
- Jérôme Lalande2
- Kamal Khujandi2
- Kamalākara Bhaṭṭa2
- Kamalākarabhaṭṭa2