| Abbreviation | Definition |
|---|---|
| OSRT | Ohio Special Response Team, Inc |
| OSSD | Organization for the Study of Sex Differences |
| OTA | Orthopaedic Trauma Association |
| OTDF | Ok Tedi Development Foundation |
| OTN | Ontario Tobacco- Free Network |
| OTS | Organization for Tropical Studies |
| OTU | Oregon Taxpayers United |
| OTWBYB | Overcoming the World by Your Believing |
| OUB | Opportunities Unlimited for the Blind |
| OUB | Opportunities Unlimited for the Blind, Inc. |
| OUI | Opportunities Unlimited, Inc. |
| OUW | Ohio United Way |
| OVA | Organisation for Visual Arts |
| OVCO | Orphan and Vulnerable Children Organisation |
| OVERT | Ontario Volunteer Emergency Response Team |
| OVF | Ohio Valley Federation |
| OVF | Oklahoma Venture Forum |
| OVI | Objectively Verifiable Indicators |
| OVP | Office of Volunteer Personnel |
| OWA | Old Whitgiftian Association |