Author
- Johannes Milis1
- John Burgh1
- John Capgrave1
- John Gower1
- John Mandeville1
- John XXII1
- John of Genoa1
- John of Seville ?1
- Jordan von Quedlinburg1
- Judah ben Saul ibn Tibbon1
- Junayd ibn Sandal Baghdādī1
- Kamal Khujandi1
- Kamal al-Din ibn al-Humam1
- Khayr al-Dīn Khalīl1
- Khālid ibn ʻAbd Allāh al-Azharī1
- Laurent d'Orleans1
- Leo I1
- Leon Battista Alberti1
- Leonardo Mainardi1
- Luca Pacioli1