| Glossary Term starting with U |
| Search SeaLifeBase |
| Ubiquitous |
| Ultimate |
| Ultimobranchial gland |
| Ultra- |
| Ultra-abyssal zone |
| Ultrahaline |
| Ultraplankton |
| Umbilical cord |
| Umbrella species |
| Unavailable nomenclatural act |
| Unavailable work |
| Uncertainty |
| Uncinate |
| Unculiferous |
| Unculus |
| Undershot |
| Undersized |
| Underslung |
| Undifferentiated coastline |
| Undulating |
| Uni- |
| Unicaniculate |
| Unicornfishes |
| Unicuspid |
| Unidentified |
| Uniformitarianism |
| Uninomen |
| Uninominal name |
| Uniserial |
| Unisexual |
| Unisexual fish |
| Unit stock |
| Unite |
| United |
| Univalve |
| Universal Resource Locator |
| Universal trawl |
| Universidade Federal de Pernambuco |
| University Museum of Zoology, Cambridge |
| University Museum, Tokyo |
| University of Alabama |
| University of Alabama, Department of Biology |
| University of Alaska at Juneau |
| University of Alaska Museum |
| University of Alberta |
| University of Arizona Museum |
| University of Arkansas Fayetteville, North Carolina |
| University of British Columbia Fish Museum, Vancouver |
| University of California Fish Museum, Santa Barbara |
| University of Central Florida, Orlando |
| University of Colorado Museum, Colorado |
| University of Connecticut Ichthyology Museum, Connecticut |
| University of Florida |
| University of Georgia Museum of Natural History, Georgia |
| University of Guam |
| University of Guyana, Center for the Study of Biological Diversity |
| University of Kansas Museum of Natural History, Kansas |
| University of Louisville, Kentucky |
| University of Maine, Orono, Maine |
| University of Massachusetts Dartmouth, Massachusetts |
| University of Miami, Rosenstiel School of Marine Science, Miami |
| University of Michigan Museum of Zoology, Michigan |
| University of Mississippi, Mississippi |
| University of Nebraska at Omaha, Nebraska |
| University of Nebraska State Museum, Division of Zoology, Nebraska |
| University of Nevada at Reno, Nevada |
| University of New Orleans Vertebrate Collection, Louisiana |
| University of North Carolina Institute of Marine Sciences, North Carolina |
| University of North Carolina, Charlotte |
| University of Puerto Rico Department of Marine Sciences, Puerto Rico |
| University of Rhode Island, Department of Zoology, Kingston |
| University of Richmond, Virginia |
| University of South Florida, Tampa, Florida |
| University of Southern Mississippi |
| University of Southern Mississippi, Hattiesburg, Mississippi |
| University of Tennessee, Knoxville |
| University of Texas at Arlington, Merriam Museum |
| University of the Ryukyus Museum, Okinawa |
| University of the South Pacific, Fiji |
| University of Tokyo, Department of Zoology, University Museum, Tokyo |
| University of Washington, Seattle |
| University of West Florida Collection, Pensacola, Florida |
| University of Wisconsin at Milwaukee, Wisconsin |
| University of Wisconsin Zoological Museum, Wisconsin |
| University of Wyoming at Laramie, Wyoming |
| Univoltine |
| Unjustified emendation |
| Unpaired fins |
| Unsegmented |
| Uo-dango |
| Uo-miso |
| UOG |
| Upland |
| Upper eyelid |
| Upper jaw length |
| Upper limb |
| Upper origin |
| Upper postventral margin |
| Uppsala University, Zoological Museum, Uppsala, Sweden |
| Upwelling |
| Urea |
| Urochordata |
| Urodermal |
| Urogenital duct |
| Urogenital papilla |
| Urogenital region |
| Uroneural |
| Urophore |
| Uropods |
| Urosome |
| Urostyle |
| Usable stock |
| Uterine cannibalism |
| Uterus |
| Utilitarianism |
| Utriculus |
| Uvula |