Ceratoserolis is a genus of isopods in the family Serolidae from the Southern Ocean around Antarctica and some Sub-Antarctic Islands.

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.

[2][3] They were once considered to be part of the genus Serolis and for a long time only Ceratoserolis trilobitoides was recognized.

[2][3][4] Because Ceratoserolis are widespread, locally abundant and relatively large for isopods, they have often been studied and used as model organism for the Antarctic region.

[3] They are slow-maturing, only breed once in their life, and the eggs and young are brooded for an extended period—almost two years—in the female's marsupium.