| Abbreviation | Definition |
|---|---|
| OHF | Oxford Hair Foundation |
| OHH | Operation Holiday Help |
| OHN | Ohio History Network |
| OHP | Office of Historic Preservation |
| OHP | Oregon Health Plan |
| OHPA | Ontario Health Providers Alliance |
| OHPCO | Ohio Hospice and Palliative Care Organization |
| OHS | Ohio Historical Society |
| OHS | Oregon Humane Society |
| OHS | Organ Historical Society |
| OHTF | Ohio Housing Trust Fund |
| OI | Osteogenesis Imperfecta |
| OI | Outreach International |
| OICD | Optometric Institute and Clinic of Detroit |
| OIF | Office for Intellectual Freedom |
| OIF | Osteogenesis Imperfecta Foundation |
| OIH | Ohio Industries for the Handicapped |
| OIN | Open Invention Network |
| OIV | Organizzazione Internazionale della Vigna e del Vino (International Organisation of Vine and Wine) |
| OJB | Oscar Joel Bryant Foundation |