- Nuns1
- Occultism--Religious aspects1
- Occultism--Religious aspects--Islam1
- Octavia, Empress, consort of Nero, Emperor of Rome, approximately 42-621
- Octoechos (Orthodox Eastern Church)1
- Odilo, Saint, Abbot of Cluny, 962-1048 or 10491
- Odo, Saint, Abbot of Cluny, approximately 879-9421
- Oedipus (Greek mythological figure)1
- Orden de Alcántara1
- Order of the Garter2
- Orthodox Eastern Church1
- Painted bindings1
- Pakhomiĭ Logofet, monk, active 15th century1
- Palm-leaf manuscripts1
- Palmistry2
- Papacy2
- Paraphrases1
- Passion of Jesus Christ4
- Pastoral theology3
- Pastoral theology--Catholic Church1