| OPAC | Ocean Policy Advisory Council 
| Others |
| OPAC | Office of Public Affairs and Communications
| Others |
| OPAC | Office Proficiency Assessment and Certification
| Others |
| OPAC | Office Proficiency Assessment Certification
| Others |
| OPAC | Officina Prototipi Automobili Carrozzeria
| Others |
| OPAC | Often People Access the Catalog
| Others |
| OPAC | Oh, Please Accept Checks
| Others |
| OPAC | Oil Producing Arab Countries
| Others |
| OPAC | Online Patron Access Catalog
| Others |
| OPAC | Online Public Access Catalog
| Others |
| OPAC | Online Public Access Catalogue
| Others |
| OPAC | Online Public Access Computer
| Others |
| OPAC | Only Public Access Content
| Others |
| OPAC | Ontario Property Assessment Corporation
| Others |
| OPAC | Open Problems in Algebraic Combinatorics
| Others |
| OPAC | Open Public Access Catalog
| Others |
| OPAC | Optimization Policies for Adaptive Control
| Others |
| OPAC | Orpheum Performing Arts Center
| Others |
| OPAC | OSU Peroperative Assessment Clinic
| Others |
| OPAC | OSU Preoperative Assessment Center
| Others |
| OPAC | Ottoson Parent Advisory Council
| Others |
| OPAC | Ouachita Parish Alternative Center
| Others |
| OPAC | Outgrowing Power Anger Control
| Others |
| OPAC | Outside Plant Access Cabinet
| Others |
| OPAC | Oval Pipes Air Conditioner
| Others |
| OPAC | Overtown Performing Arts Center
| Others |
| OPAC | Oxford Performing Arts Center
| Others |