| Abbreviation | Definition |
|---|---|
| ULFI | United Leukodystrophy Foundation, Inc. |
| ULPA | United Lightning Protection Association |
| ULRA | Universal Living Rosary Association |
| UMCCC | University of Michigan Comprehensive Cancer Center |
| UME | United Marriage Encounter |
| UMOC | United Millennials of Canada |
| UNA | United Nations Association of the USA |
| UNAA | Ugandan North American Association |
| UNAB | Uganda National Association for the Blind |
| UNAUSA | United Nations Association of the United States of America |
| UNCA | United Neighborhood Centers of America |
| UNCAI | United Neighborhood Centers of America, Inc. |
| UNCRPD | United Nations Convention on the Rights of Persons wiith Disability |
| UNDP | United Nations Development Programme |
| UNFPA | United Nations Fund for Population Activities |
| UNIA | Universal Negro Improvement Association |
| UNICEF | United Nations International Children's Emergency Fund |
| UNITY | United National Indian Tribal Youth |
| UNITY | United National Indian Tribal Youth, Inc. |
| UNO | United Neighborhood Organization |