| Abbreviation | Definition |
|---|---|
| OLC | On Line Contest |
| OLP | Officially Licensed Product |
| OLR | On-Line Racing |
| OLW | On- Line Warfare Gaming League |
| OM | Olympic Mountaineering |
| OM | Olympique de Marseille |
| OMA | One Man Army |
| OMC | One Man Crew |
| OMEGA | Organization Of Modern Extreme Grappling Artists |
| OMH | Oshawa Minor Hockey |
| OMHA | Ontario Minor Hockey Association |
| OMHA | Oshawa Minor Hockey Association |
| OMR | Old Man Racing |
| OMSN | Ole Miss Sports News |
| OMSP | Ole Miss Sports Productions |
| ONC | Oregon Nordic Club |
| ONMC | Official NASCAR Members Club |
| OO | Open Optionals |
| OOB | Out Of Bounds |
| OOC | Ogden Outdoor Coalition |