The Ophuroidea are a class of echinoderms which includes the brittlestars. Closely related to starfish (sea stars), they display radial symmetry have a central disk-shaped body and (usually) five slender, highly flexible arms that are quite distinct from the body.

There is no replication of internal organs, as in the arms of sea stars, just one set in the central disk. Compared to starfish, brittle stars have a much smaller central disk and no anus. Wastes are eliminated through the mouth, which is situated on the underside of the disk. The name is derived from their arms breaking off as a means of defense. New arms are easily regenerated. They are also called serpent stars because of the snake-like movements of the five arms.