List of ecoregions in the United States (WWF)

The following is a list of ecoregions in the United States as identified by the World Wide Fund for Nature (WWF). The United States is a megadiverse country with a high level of endemism across a wide variety of ecosystems.

Terrestrial ecoregions
The United States is unique among countries in that its terrestrial ecoregions span three biogeographic realms: the Nearctic, Neotropical, and Oceanian realms.

50 states
Alaska is the most biodiverse state with 15 ecoregions across 3 biomes in the same realm. California comes in a close second with 13 ecoregions across 4 biomes in the same realm. By contrast, Rhode Island is the least biodiverse with just one ecoregion - the Northeastern coastal forests - encompassing the entire state.

The terrestrial ecoregions of the 50 states of the United States are as follows:

5 inhabited territories
The ecoregions of the 5 inhabited territories of the United States are as follows:

Marine ecoregions
The marine ecoregions of the 50 states of the United States are as follows: