| Abbreviation | Definition |
|---|---|
| OJM | Oregon Jewish Museum |
| OMA | Oceanside Museum of Art |
| OMA | Oklah Museums Association |
| OMA | Orlando Museum of Art |
| OMAA | Ogunquit Museum of American Art |
| OMAH | Orillia Museum of Art and History |
| OMAM | Ormond Memorial Art Museum |
| OMMC | Organization of Military Museums of Canada |
| OMN | Oklahoma Museum Network |
| OMOT | Ohio Museum of Transportation |
| OMSA | Ogden Museum of Southern Art |
| OMSI | Oregon Museum of Science and Industry |
| OMWB | Oakland Museum Women's Board |
| ONM | Osage Nation Museum |
| OOTB | Out Of The Book |
| OPH | Old Parliament House |
| OSHM | Old State House Museum |
| OSHM | Outdoor Sporting Heritage Museum |
| OSMOSA | Open Source Museum of Open Source Art |
| OTM | Owlshead Transportation Museum |