- Kingdom: Animalia
- Phylum: Chordata
- Class: Aves
- Order: Charadriiforme
- Family: Laridae
- Genus: Sternula
- Species: antillarum
- Subspecies: athalassos
The Least Tern is divided into three subspecies:
- Sternula antillarum brownie: The California Least Tern nests along the Pacific Coast of California
- Sternula antillarum athalassos: The Interior Least Tern nests along river systems in the interior of the United States.
- Sternula antillarum antillarum: The Coastal Least Tern nests along the Atlantic Coast.