Echinoderms are invertebrate marine animals that are found in all oceans of the world and at all depths. There are no echinoderms in freshwater environments.

Members of the Phylum Echinodermata include many easily recognizable creatures such as sea stars (or starfish), brittle stars, sea urchins, sea cucumbers, and sea lilies. All of these animals are radially or biradially symmetric, and they fill a variety of niches in marine environments as particle feeders, browsers, scavengers, and predators.