word | | Country name |
| unofficial | Laos | conventional long form: Lao People's Democratic Republic conventional short form: Laos local long form: Sathalanalat Paxathipatai Paxaxon Lao local short form: Pathet Lao (unofficial) |
| Upper | Burkina Faso | conventional long form: none conventional short form: Burkina Faso local long form: none local short form: Burkina Faso former: Upper Volta, Republic of Upper Volta |
| Urdun | Jordan | conventional long form: Hashemite Kingdom of Jordan conventional short form: Jordan local long form: Al Mamlakah al Urduniyah al Hashimiyah local short form: Al Urdun former: Transjordan |
| Urduniyah | Jordan | conventional long form: Hashemite Kingdom of Jordan conventional short form: Jordan local long form: Al Mamlakah al Urduniyah al Hashimiyah local short form: Al Urdun former: Transjordan |
| Uruguay | Uruguay | conventional long form: Oriental Republic of Uruguay conventional short form: Uruguay local long form: Republica Oriental del Uruguay local short form: Uruguay former: Banda Oriental, Cisplatine Province |
| Urundi | Burundi | conventional long form: Republic of Burundi conventional short form: Burundi local long form: Republique du Burundi/Republika y'u Burundi local short form: Burundi former: Urundi |
| US | Burma | ... Union of Burma conventional short form: Burma local long form: Pyidaungzu Myanma Naingngandaw (translated by the US Government as Union of Myanma and by the Burmese as Union of Myanmar) local short ... |
| US | United States | conventional long form: United States of America conventional short form: United States abbreviation: US or USA |
| USA | United States | conventional long form: United States of America conventional short form: United States abbreviation: US or USA |
| used | Macedonia | ... short form: Macedonia local long form: Republika Makedonija local short form: Makedonija note: the provisional designation used by the UN, EU, and NATO is the "former Yugoslav Republic of Macedonia" (FYROM) former ... |
| USVI | Virgin Islands | conventional long form: United States Virgin Islands conventional short form: Virgin Islands former: Danish West Indies abbreviation: USVI |