Ceratostoma, common name the "hornmouth" snails, is a genus of medium to large predatory sea snails, marine gastropod mollusks in the family Muricidae, the rock snails.

This genus should not be confused with the nudibranch genus Ceratosoma, meaning "thorn body". Ceratostoma means "thorn mouth" because of the thornlike projection on the edge of the aperture, used as a tool in predation to prop open the shells of bivalves and barnacles.

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