| Abbreviation | Definition |
|---|---|
| OFCC | Our Fellowship Christian Church |
| OFL | Out of Friendship and Love |
| OFM | Order Of Franciscans Minor |
| OFM | Ordo Fratrum Minorum |
| OFS | Ordine Francescano Secolare |
| OG | Olympian Gods |
| OG | One God |
| OGS | Oratory of the Good Shepherd |
| OGT | Oakwood Gospel Tabernacle |
| OGW | Outer Gate Wicca of SW Florida |
| OHC | Open House Church |
| OHCC | Oak Hill Christian Center |
| OHT | Ohr HaTorah |
| OIC | Organisation of the Islamic Conference |
| OIC | Organization for Islamic Cooperation |
| OIC | Organization of the Islamic Conference |
| OICS | Orcas Island Christian School |
| OIEF | Oulu International Evangelical Fellowship |
| OKI | Organisasi Kerja Sama Islam |
| OLB | Oaf Like Bread |