Coelenterata is an obsolete term encompassing two animal phyla, the Ctenophora (comb jellies) and the Cnidaria (coral animals, true jellies, sea anemones, sea pens, and their allies).

The name comes from the Greek koilos, "full bellied", referring to the hollow body cavity common to these two phyla. They have very simple tissue organization, with only two layers of cells, external and internal.