Thalasseus maximus, commonly known as the Royal Tern, is primarily native to the coastal regions of the Americas. It is commonly found along the eastern coast of North America, from the mid-Atlantic United States down to the Caribbean. It is also present along the Gulf of Mexico, throughout Central America, and along the northern and central coasts of South America. In addition, the Royal Tern is seen along the western coast of Africa, from Senegal to Namibia.

The Royal Tern typically inhabits coastal environments. It prefers sandy beaches, mudflats, and estuaries, often nesting on islands that offer some protection from predators. The climate in these areas ranges from temperate to tropical, with a preference for warm weather conditions. During the breeding season, they are usually found on flat, low-lying islands with sparse vegetation.

As a coastal bird, the Royal Tern occupies an ecological niche that involves feeding primarily on fish, which it catches by diving into the water. It is adapted to marine and estuarine ecosystems, where it plays a crucial role as both predator and prey. Its presence is indicative of a healthy marine environment and it is often seen in mixed-species flocks with other terns and seabirds. Variations in habitat may occur due to regional adaptations, such as differing availability of nesting sites and food resources.