| Abbreviation | Description |
| UDEAC | Central African Customs and Economic Union |
| UHF | ultra-high-frequency |
| UK | United Kingdom |
| UN | United Nations |
| UNAMA | United Nations Assistance Mission in Afghanistan |
| UNAMIR | United Nations Assistance Mission for Rwanda |
| UNAMSIL | United Nations Mission in Sierra Leone |
| UNAVEM III | United Nations Angola Verification Mission III |
| UNCLOS | United Nations Convention on the Law of the Sea, also know as LOS |
| UNCRO | United Nations Confidence Restoration Operation in Croatia |
| UNCTAD | United Nations Conference on Trade and Development |
| UNDCP | United Nations Drug Control Program |
| UNDOF | United Nations Disengagement Observer Force |
| UNDP | United Nations Development Program |
| UNEP | United Nations Environment Program |
| UNESCO | United Nations Educational, Scientific, and Cultural Organization |
| UNFICYP | United Nations Peace-keeping Force in Cyprus |
| UNFPA | United Nations Population Fund |
| UNHCR | United Nations High Commissioner for Refugees |
| UNHCRHR | United Nations High Commissioner for Human Rights |
| UNICEF | United Nations Children's Fund |
| UNICEP | United Nations International Comparison Program |
| UNICRI | United Nations Interregional Crime and Justice Research Institute |
| UNIDIR | United Nations Institute for Disarmament Research |
| UNIDO | United Nations Industrial Development Organization |
| UNIFIL | United Nations Interim Force in Lebanon |
| UNIKOM | United Nations Iraq-Kuwait Observation Mission |
| UNITAR | United Nations Institute for Training and Research |