| Abbreviation | Definition |
|---|---|
| UNODC | United Nations Office On Drugs and Crime |
| UNOS | United Network for Organ Sharing |
| UNPA | University Neighborhood Preservation Association |
| UOA | United Ostomy Association |
| UOAI | United Ostomy Association, Inc. |
| UOIF | Union des Organisations Islamiques de France (French: Union of Islamic Organizations in France) |
| UOS | Under One Sun |
| UPC | United Poultry Concerns |
| UPEC | Upper Peninsula Environmental Coalition |
| UPICA | Uttar Pradeshies In Canada |
| UPLF | Universal Proutist Labour Federation |
| UPRD | United Peace Relief Detroit |
| URAC | Utilization Review Accreditation Commission |
| URFLY | Urban Youth Financial Literacy Foundation |
| URM | Union Rescue Mission |
| URPA | United Rail Passenger Alliance |
| URPA | Utah Parks and Recreation Association |
| URPS | Utahns for Responsible Public Spending Records |
| USA | United Self Assistance |
| USA | United Smokers Association |