| Ulmus intermedia | Ulmus ismaelis | Ulmus keia-ki |
| Ulmus kijimana | Ulmus laciniata | Ulmus laevigata |
| Ulmus laevis | Ulmus lamellosa | Ulmus lanceifolia |
| Ulmus lesueurii | Ulmus leucocarpa | Ulmus leucosperma |
| Ulmus longifolia | Ulmus macrocarpa | Ulmus major |
| Ulmus mesocarpa | Ulmus mexicana | Ulmus mianzhuensis |
| Ulmus microcarpa | Ulmus microphylla | Ulmus minor |
| Ulmus modiolina | Ulmus mollifolia | Ulmus monumentalis |
| Ulmus mossii | Ulmus multinervosa | Ulmus nana |
| Ulmus nemoralis | Ulmus nemorosa | Ulmus nervosa |
| Ulmus nigra | Ulmus nitens | Ulmus nuda |
| Ulmus oblongata | Ulmus obovata | Ulmus octandra |
| Ulmus ontariensis | Ulmus opaca | Ulmus parvifolia |
| Ulmus pinguis | Ulmus pitteursii | Ulmus planereoides |
| Ulmus polygama | Ulmus procera | Ulmus prunifolia |
| Ulmus pseudopropinqua | Ulmus pseudosuberosa | Ulmus pumila |
| Ulmus purpurea | Ulmus pyramidalis | Ulmus reticulata |
| Ulmus rosseelsii | Ulmus rotundata | Ulmus rotundifolia |
| Ulmus rubra | Ulmus rubrocarpa | Ulmus sarniensis |
| Ulmus scampstoniensis | Ulmus serotina | Ulmus sparsa |
| Ulmus superba | Ulmus surculosa | Ulmus szechuanica |
| Ulmus tetrandra | Ulmus thomasii | Ulmus tiliifolia |
| Ulmus tomentosa | Ulmus tortuosa | Ulmus transbaicalensis |
| Ulmus tridens | Ulmus triserrata | Ulmus urticifolia |
| Ulmus uyematsui | Ulmus vegeta | Ulmus villosa |
| Ulmus virens | Ulmus viscosa | Ulmus vulgaris |
| Ulmus wallichiana | Ulmus wallichii | Ulmus webbiana |
| Ulna | Ulnar artery | Ulnar nerve |
| Ulnar veins | Ulrich Becher | Ulrich Borowka |
| Ulrich Jasper Seetzen | Ulrich Ramé | Ulrich van Gobbel |
| Ulrich von Hutten | Ulrich Wehling | Ulrichite |
| Ulrika Ågren | Ulrike Meinhof | Ulrike Richter |
| Ulsan Hyundai FC | Ulster | Ultimate Fighting Championship |
| Ultimate Mortal Kombat 3 | Ultimate Pro Wrestling | Ultimate Spider-Man (TV series) |
| Ultimate tensile strength | Ultimatum | Ultimatum game |
| Ultra | Ultra Games | Ultra high frequency |
| Ultra-leftism | Ultrabook | Ultracold atom |
| Ultracold neutrons | Ultrafiltration | UltraISO |
| Ultralight aviation | Ultraluminous X-ray source | Ultramicroscope |
| Ultrasonic cleaning | Ultrasonic motor | Ultrasonic testing |
| Ultrasound | Ultrasound energy | Ultrastructure |
| Ultraviolet | Ultraviolet astronomy | Ultraviolet catastrophe |
| Ultraviolet germicidal irradiation | Ultraviolet index | Ultraviolet-visible spectroscopy |
| Ulu'l azm prophets | Uluç Ali Reis | Ulugbek Bakayev |
| Ulugh Beg | Ulugh Beg Observatory | Ululation |
| Ulva | Ulva costata | Ulva cuneata |
| Ulva cylindrica | Ulva digitata | Ulva lactuca |
| Ulva purpurascens | Ulva umbilicata | Ulvaceae |
| Ulvales | Ulvina | Ulvophyceae |
| Ulyanovsk | Ulysses (spacecraft) | Ulysses S. Grant |
| Ulysses, Kansas | Ulysses, Nebraska | UM Airlines |
| Uma | Uma Thurman | Umaga (wrestler) |
| Umar | Umar al-Tilmisani | Umar Farouk Abdulmutallab |
| Umar Khan | Umar Muhayshi | Umar Sulaiman Al-Ashqar |
| Umaru Musa Yar'Adua | Umatilla, Florida | Umayyad |
| Umayyad architecture | Umayyad Caliphate | Umayyad Empire |
| Umayyad invasion of Gaul | Umayyad Mosque | Umayyads |
| Umber View Heights, Missouri | Umberto Caligaris | Umberto Eco |
| Umberto Rizzitano | Umbilical artery | Umbilical cord |
| Umbilical plane | Umbilical vein | Umbilical vesicle |
| Umbiliceae | Umbilicus | Umbilicus botryoides |
| Umbilicus chloranthus | Umbilicus citrinus | Umbilicus erectus |
| Umbilicus giganteus | Umbilicus heylandianus | Umbilicus horizontalis |
| Umbilicus intermedius | Umbilicus luteus | Umbilicus parviflorus |
| Umbilicus rupestris | Umbilicus samium | Umbilicus simplex |
| Umbilicus tropaeolifolius | Umbrella | Umbrella term |
| Umbria | UMD | UML |
| UML Model | UML Model diagram | Umm al-Fahm |
| Umm al-Qura Mosque | Umm Nidal | Umma Party (Egypt) |
| Ummahfilms | Umniah | Umrah |
| UMTS Terrestrial Radio Access Network | UMTS المراجعة 8 | Umurbek Bazarbayev |
| Umut Bulut | UN | Un Certain Regard |
| UN Commission on Human Rights | Un drame au Mexique | Un gallo con muchos huevos |
| Un homme et une femme | UN number | Un Paso Adelante (TV series) |
| UN Peacemaker | UN Women | UN-Water |
| Unaccompanied minor | Unadilla (village), New York | Unadilla Township, Michigan |
| Unadilla, Georgia | Unadilla, Nebraska | Unai Alba |
| Unai Emery | Unai Expósito | UNAIDS |
| Unalakleet, Alaska | Unalaska, Alaska | UNAM |
| Unary operation | Unas | UNASUR |
| Unbalanced line | Unbarred spiral galaxy | Unbreakable |
| Unbreakable (film) | Uncaria tomentosa | Uncertainty |
| Uncertainty principle | Uncharted | Uncharted 2: Among Thieves |
| Uncharted 3: Drake's Deception | Uncharted 4: A Thief's End | Uncharted: Drake's Fortune |
| Uncharted: Golden Abyss | Uncia uncia | Uncinaria |
| Uncinaria hamiltoni | Uncinaria rauschi | Uncinaria sanguinis |
| Uncinaria stenocephala | Uncinaria yukonensis | Uncinate process of ethmoid bone |
| Uncinate process of vertebra | Uncle Grandpa | Uncle Sam |
| Uncombable hair syndrome | Unconditional surrender | Unconscious mind |
| Unconsciousness | Uncontrolled airspace | Unconventional computing |
| Uncoupling (neuropsychopharmacology) | Uncus | Uncyclopedia |
| Undaria pinnatifida | Undecane | Undecylenic acid |
| Under Ash | Under Siege (2005 video game) | Under the Bombs |
| Underarm hair | Underconsumption | Underemployment |
| Undergarment | Undergraduate | Undergraduate education |
| Underhill, Vermont | Underhill, Wisconsin | Undernet |
| Understanding | Underwater photography | Underwater search and recovery |
| Underwood's septa | Underwood, Iowa | Underwood, Minnesota |
| Underwood, North Dakota | Underworld (1927 film) | Underworld: Awakening |
| Underworld: Evolution | Underwriting | Undifferentiated connective tissue disease |
