- U ... U.S.A.
- U.S.S.R. ... UBV system
- Ubykh language ... Udi Plateau
- Udi-Nsukka Plateau ... Ugarte, Augusto Pinochet
- UGCC ... Ujong Salang
- Ujung Kulon National Park ... ULCA
- ULCC ... Ulster Defence Regiment
- Ulster Democratic Party ... ultraviolet photoelectron spectroscopy
- ultraviolet photography ... umbilical artery
- umbilical cord ... Umuahia
- umuganuro ... Uncle Buck
- Uncle Dan ... underclay
- underconsumption theory ... underwool
- Underworld ... Ungewitter, Richard
- Unggi ... uniformity
- Uniformity, Acts of ... Union Nationale
- Union Nationale Camerounaise ... unit electrical charge
- unit heater ... United Farm Workers of America
- United Farmers of Ontario ... United Nations Peace-Keeping Force in Cyprus
- United Nations Peacekeeping Forces ... United States Coast Guard Academy
- United States Commission of Fish and Fisheries ... United States presidential election of 1912
- United States presidential election of 1916 ... United Steelworks Co.
- United Struggle ... Universal Orlando Resort
- Universal Pictures ... Unknown Girl, The
- Unknown Known, The ... Unser, Alfred
- Unser, Bobby ... uomo che andrà in America, L’
- uomo come fine, L’ ... Upolu
- uposatha ... UPRONA
- Uprooted, The ... uranium hexafluoride
- uranium hydride ... Urbino, Lorenzo di Piero de’ Medici, duca di
- Urbinum Hortense ... urination
- urine ... Urso
- Urso, Camilla ... Usages of Barcelona
- USAI ... Usnea barbata
- Usnea florida ... Ut queant laxis
- Ut unum sint ... Utopia
- Utopia 14 ... Uvularia grandiflora
- Uvularia perfoliata ... Uzziah
