Encyclopedias, Almanacs, Transcripts, and Maps
- Orense
- Orenstein, Alexander Jeremiah
- Orenstein, Arbie
- Orgad (Bueshel) ben Zion
- Organ, Liturgical Use of
- Organicism
- Organization of the Islamic Conference
- Orgelbrand, Samuel
- Orgeyev
- Orḥot Ḥayyim
- Orḥot Ẓaddikim
- Oria
- Oriental Literature
- Orientalists
- Origen and Origenism
- Origen°
- Original Enlightenment (Hongaku)
- Original Justice
- Orihuela
- Oriol, Joseph, St.