Ceratoserolis is a genus of isopods in the family Serolidae from the Southern Ocean around Antarctica and some Sub-Antarctic Islands. They prefer to live on soft bottoms and range of least between 24 and 950 m (80–3,120 ft) in depth. They are superficially similar to the unrelated, extinct trilobites (hence the specific name trilobitoides for the first described species) and reach up to about 8 cm (3.1 in) in length. They were once considered to be part of the genus Serolis and for a long time only Ceratoserolis trilobitoides was recognized. The validity of the other species has been disputed, but there are some morphological and genetic differences between them and C. trilobitoides, and there are indications that additional, currently unrecognized species of Ceratoserolis exist.