Encyclopedias, Almanacs, Transcripts, and Maps
- O'Toole, George Barry
- O? Ma?i Padme Hu?
- Oak, Synod of the
- Oates Plot
- Oath More Judaico or Juramentum Judaeorum
- Oaths (in the Bible)
- Oaths, English Post-Reformation
- Obadiah, The Norman Proselyte
- Obadya, Abraham
- Obazine (Aubazine), Abbey of
- Obed
- Obed-Edom
- Obedas°
- Obediential Potency
- Obermann, Julian Joël
- Obermeyer, Jacob
- Obernai
- Obernik, Judah
- Oblate Sisters of Providence
- Oblate Sisters of St. Francis de Sales