- U ... Ubaldini, Ruggieri degli
- Ubange-Uele plateau ... Uchida, Mitsuko
- Uchimura Kanzō ... Udržal, František
- UDSR ... Ugric languages
- UGT ... Ukraine scandal
- Ukraine, flag of ... Uljanovsk
- Uljanovsk ... Ultimate Good Luck, The
- ultimate tensile stress ... Ulvophyceae
- Ulyanov, Vladimir Ilich ... Umbriel
- Umbrisol ... UNAMIR
- Unamuno y Jugo, Miguel de ... unctio extrema
- unction ... undersea transportation
- undershot waterwheel ... unevenly-grained rock
- UNEXIM ... uniface blade
- unifacial tool ... union dues
- Union Économique Benelux ... Unionidae
- unionism ... United Automobile Workers of America
- United Automobile, Aircraft and Agricultural Implement Workers of America ... United Nations Convention on the Law of the Sea
- United Nations Convention to Combat Desertification ... United States
- United States Agency for International Development ... United States presidential election of 1789
- United States presidential election of 1792 ... United States v. O’Brien
- United States v. Rabinowitz ... universal generalization
- Universal German Educational Institute ... University College, London
- university extension ... UNRISD
- unrounded vowel ... Untwine
- ununbium ... UPI
- UPIAS ... Uppland, law of
- Uppsala ... Uralskie Gory
- Uralskie Mountains ... Urban, Keith
- Urban, Keith Lionel ... uridylic acid
- Uriel ... Ursa Major cluster
- Ursa Minor ... USA Volleyball
- USA Water Ski ... Usman dan Fodio
- Usman, Dokka Abu ... UT
- Ut de Franzosentid ... Utopia
- utopia ... Uvularia perfoliata
- uvularization ... Uzziah
