Orbicella annularis, commonly known as the Boulder star coral, is a species of coral that lives in the western Atlantic Ocean and is the most thoroughly studied and most abundant species of reef-building coral in the Caribbean to date. It also has a comprehensive fossil record within the Caribbean. This species complex has long been considered a generalist that exists at depths between 0 and 80 m and grows into varying colony shapes (heads, columns, plates) in response to differing light conditions. Only recently with the help of molecular techniques has O. annularis been shown to be a complex of at least three separate species. Those species are divided into O. annularis, O. faveolata, and O. franksi. This coral was originally described as Montastraea annularis.