Roman Catholic and Orthodox churches: General Biographies
- John Carroll
- John Cassian
- John England
- John Gerson
- John Henry Newman
- John Ireland (archbishop)
- John Joseph Hughes
- John Joseph OConnor
- Jose de Anchieta
- Joseph Cardinal Bernardin
- Juan de Torquemada
- Juan de Zumarraga
- Junipero Serra
- Kateri Tekakwitha
- Lanfranc
- Marcion
- Marcus Minucius Felix
- Margery Kempe
- Marianus Scotus
- Marie de lIncarnation