| Abbreviation | Definition |
|---|---|
| POCU | Post Office Credit Union |
| POEU | Post Office Engineering Union |
| POPCRU | Police and Prisons Civil Rights Union |
| POREA | Port Office Regional Employees Association |
| POSU | Private Oil Sector Union |
| POTWA | Post and Telecommunication Workers Union |
| PPMU | Public Policy Majors Union |
| PPU | Peace Piedge Union |
| PPU | Peace Pledge Union |
| PPU | Picture Perfect Union |
| PPU | Professional Pilots Union |
| PRCU | Polish Roman Catholic Union |
| PRCU | Powell River Credit Union |
| PRTEU | Philadelphia Rapid Transit Employees Union |
| PRTU | Panchayat Raj Teachers Union |
| PRTU | Progressive Recognised Teachers Union |
| PRUI | Persatuan Rugby Union Indonesia |
| PRUMA | Puerto Rican Union of Mutual Aid, Inc. |
| PSAC | Public Service Alliance of Canada |
| PSEU | Public Safety Employees Union |