| Abbreviation | Definition |
|---|---|
| OK | Olympia Kiwanis |
| OKB | Offener Kanal Berlin (Open Channel Berlin) |
| OKF | Open Knowledge Foundation |
| OKF | OpenKeks-Foundation |
| OKF | Otto Kinne Foundation |
| OKF | Overseas Koreans Foundation |
| OKUP | Ovibashi Karmi Unnayan Program |
| OKV | OSCE Mission in Kosovo By-Mail Voting Programme |
| OLHSA | Oakland Livingston Human Service Agency |
| OLI | Open Learning Institute |
| OLI | Operation Lifesaver International |
| OLLA | Oakland Livingston Legal Aid |
| OLP | Onondaga Lake Partnership |
| OLV | Our Lady of Victory Homes of Charity |
| OMCRS | Outreach Mission Charitable Religious Society |
| OMCRS | Outreach Missions Charitable and Religious Society |
| OMEA | Ohio Music Education Association |
| OMKIDS | non-profit formed in uganda |
| OMN | Organizacion Mundial de Medicina Natural |
| OMRF | Oklahoma Medical Research Foundation |