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 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.