Ecoregions by country - U
Uganda
Ukraine
United Arab Emirates
United Kingdom
United States
- Alaskan North Slope Coastal Tundra
- Appalachian and Mixed Mesophytic Forests
- Bering Sea
- California Chaparral and Woodlands
- Californian Current
- Chesapeake Bay
- Chihuahuan Freshwater
- Chihuahuan-Tehuacán Deserts
- Colorado River
- Everglades Flooded Grasslands
- Grand Banks
- Greater Antillean Marine
- Gulf of Alaska Coastal Rivers and Streams
- Klamath-Siskiyou Coniferous Forests
- Lower Mississippi River
- Mississippi Piedmont Rivers and Streams
- Northern Prairie
- Pacific Northwest Coastal Rivers and Streams
- Pacific Temperate Rainforests
- Sierra Madre Oriental and Occidental Pine-Oak Forests
- Sierra Nevada Coniferous Forests
- Sonoran-Baja Deserts
- Southeastern Coniferous and Broadleaf Forests
- Southeastern Rivers and Streams
