Author
- John Cassian1
- John Chrysostom1
- John Fortescue1
- John Larry England1
- John Lydgate1
- John Mandeville1
- John Tiptoft, 1st Earl of Worcester1
- John XXII1
- John of Genoa1
- Jonathan Eybeschutz1
- Jordan von Quedlinburg1
- Joseph Haslewood1
- José Pellicer1
- Juan Martínez Silíceo1
- Khaqani1
- Kingdom of Castile1
- Laurent d'Orleans1
- Leo I1
- Leon Battista Alberti1
- Lorenzino de' Medici1