OMC
- Land Systems OMC
- OMC (band)
- OMC Shipping
- Octyl methoxycinnamate
- Odisha Mining Corporation
- Oil marketing company
- Old Man's Child
- Omnicom Group
- Ontario Medal for Good Citizenship
- Open Method of Coordination
- OpenModelica
- Operations and Maintenance Centre
- Orange Monte Carlo
- Ordem do Mérito Cultural
- Order of Civil Merit
- Ormoc Airport
- Osaka Medical College
- Outboard Marine Corporation
- Outlaw motorcycle club
- Oxfordshire Museums Council
- World Trade Organization