| Abbreviation | Definition |
|---|---|
| OMNR | Ontario Ministry of Natural Resources |
| OMP | Ontario Midwifery Program |
| OMR | Office of Mental Retardation |
| OMT | Outright Monetary Transactions |
| OMV | Office of Motor Vehicles |
| ON | ONtario |
| ONJ | Ocean, New Jersey |
| ONT.PARL | Ontario Legislative Television Satellite Network |
| ONTC | Ontario Northland Transportation Commission |
| ONTERM | Ontario Terminology (Web site of the Government Translation Service providing bilingual forms of official government names) |
| ONY | Oneonta, New York |
| OOB | Old Orchard Beach |
| OOE | Oregon Office of Energy |
| OOJ | Office Of Judges |
| OOTM | Office of the Mayor |
| OPA | Office of Public Affairs |
| OPB | Ontario Parole Board |
| OPB | Oregon Progress Board |
| OPC | Online Parish Clerk |
| OPCPCC | Ohio Patient-Centered Primary Care Collaborative |