Casatia is a genus of extinct cetacean from the Early Pliocene, approximately between 5.1 and 4.5 million years ago. The genus contains a single species, C. thermophila. It was described from a partial skull. Its closest relatives are the narwhal and beluga, yet the remains were found farther south than its relatives, supporting the theory that monodontids evolved from warm water genera before becoming adapted to cold water.