Encyclopedias, Almanacs, Transcripts, and Maps
- Organ, Liturgical Use of
- Organicism
- Organization of the Islamic Conference
- Orgelbrand, Samuel
- Orgeyev
- Oria
- Oriental Literature
- Orientalists
- Origen and Origenism
- Origen°
- Original Enlightenment (Hongaku)
- Original Justice
- Orihuela
- Oriol, Joseph, St.
- Orione, Luigi, Bl.
- Orlah
- Orland, Hershl
- Orland, Yaakov
- Orléans-Longueville, Antoinette d’
- Orlev, Uri