Index: O
- O’Brien, Ronald
- Obermeister, Ruben
- Occult
- OCRT
- Odinism
- Oekumenische Beratstellung - Religiöse Sondergrupen & Sekten
- O’Hair, Madalyn Murray
- O’Meara, Nancy
- Office of Faith-Based and Community Initiatives
- Old German Baptist Brethren
- Omega Code
- Oneness Pentecostalism
- Oneness Theology
- Ontario Consultants on Religious Tolerance
- Ontology
- Open Metaphysics
- Opus Dei
- Oral Roberts University
- Orden Fiat Lux (Uriella)
- Order of St. Charbel
- Order of the Solar Temple
- Ordo Templi Orientis
- Orthodox
- Orthodox Church
- Orthodoxy
- Orthopraxis
- OSA
- Osho
- Osteen, John
- Our Lady of Fatima
- Out of the Cocoon
- Oxford Capacity Analysis
