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.

[3] It also has a comprehensive fossil record within the Caribbean.

[4][5] This species complex has long been considered a generalist that exists at depths between 0 and 80 metres (0 and 262 ft)[6] and grows into varying colony shapes (heads, columns, plates) in response to differing light conditions.

[7] Only recently with the help of molecular techniques has O. annularis been shown to be a complex of at least three separate species.

[8][9][10] Those species are divided into O. annularis, O. faveolata, and O. franksi.