word | | Country name |
| Uganda | Uganda | conventional long form: Republic of Uganda conventional short form: Uganda |
| UK | United Kingdom | conventional long form: United Kingdom of Great Britain and Northern Ireland; note - Great Britain includes England, Scotland, and Wales conventional short form: United Kingdom abbreviation: UK |
| Ukraine | Ukraine | conventional long form: none conventional short form: Ukraine local long form: none local short form: Ukrayina former: Ukrainian National Republic, Ukrainian State, Ukrainian Soviet Socialist Republic |
| Ukrainian | Ukraine | conventional long form: none conventional short form: Ukraine local long form: none local short form: Ukrayina former: Ukrainian National Republic, Ukrainian State, Ukrainian Soviet Socialist Republic |
| Ukrayina | Ukraine | conventional long form: none conventional short form: Ukraine local long form: none local short form: Ukrayina former: Ukrainian National Republic, Ukrainian State, Ukrainian Soviet Socialist Republic |
| Uls | Mongolia | conventional long form: none conventional short form: Mongolia local long form: none local short form: Mongol Uls former: Outer Mongolia |
| Uman | Oman | conventional long form: Sultanate of Oman conventional short form: Oman local long form: Saltanat Uman local short form: Uman former: Muscat and Oman |
| Umbuso | Swaziland | conventional long form: Kingdom of Swaziland conventional short form: Swaziland local long form: Umbuso weSwatini local short form: eSwatini |
| UN | 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: People's Republic ... |
| Unidos | Mexico | conventional long form: United Mexican States conventional short form: Mexico local long form: Estados Unidos Mexicanos local short form: Mexico |
| Union | Burma | conventional long form: 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 ... |