| Abbreviation | Definition |
|---|---|
| UNHRC | United Nations Human Religious Commission |
| UNINUS | Universitas Islam Nusantara |
| UNIS | Universitas Islam Syekh-Yusuf |
| UNISBA | Universitas Islam Bandung |
| UNISMA | Universitas Islam Malang |
| UNISSULA | Universitas Islam Sultan Agung |
| UNIZAR | Universitas Islam Al Azar |
| UOB | Unity Of Beaverton Church |
| UOC | Ukrainian Orthodox Church |
| UOCC | Ukrainian Orthodox Catholic Church |
| UOC-MP | Ukrainian Orthodox Church-Moscow Patriarchate |
| UOCUS | Ukrainian Orthodox Church of the United States |
| UOC-USA | Ukrainian Orthodox Church of the United States of America |
| UOF | Unity Of Fairfax Church |
| UOIF | Union des Organisations Islamiques de France (French: Union of Islamic Organizations in France) |
| UOM | Unity of Man Church |
| UOR | Union of Orthodox Rabbis |
| UOU | Universal Oneness United |
| UOV | Unity of Venner Church |
| UPA | Ulster Protestant Action |