| Abbreviation | Definition |
|---|---|
| OPPF | Olof Palme Peace Foundation |
| OPPFB | Office of Programme Planning, Finance and Budget |
| OPR | Operational Peer Review |
| OPS | Office of Programme Services |
| OSE | Office of Special Envoy |
| OSL | Offshore Leak (Off-shore leak 2012) |
| OTCD | Organizations of Turkic Cooperation and Development |
| OUN | Organization of United Nations |
| P5 | Permanent 5 |
| PAAS | Project Accrual and Accountability System |
| PAIR | Political Asylum Immigration Representation |
| PAJ | Port Authority of Jersey |
| PASMUN | Pan American School Model of the United Nations |
| PBIED | Person-Borne Improvised Explosive Device |
| PC | Peaceful Coexistance |
| PCARC | Project Cooperation Agreement Review Committee |
| PCDA | Provisional Committee on proposals related to a WIPO Development Agenda |
| PCG | Pro-China Government |
| PCMU | Programme Coordinating and Monitoring Unit |
| PCPG | People and Change Practice Group |