Ceratosoma trilobatum is a species of colorful dorid nudibranch, a sea slug, a shell-less marine gastropod mollusk in the family Chromodorididae.

It is widespread throughout the tropical waters of the Indo-Pacific area, from the oriental African coast to Japan, Red Sea included.

However, the body colouration is not a valuable criterion of determination for this species because it can easily be confused with Ceratosoma tenue.

[4] Another specificity of the species is the kind of "horn" covering the gills, which is like a lure and acts as a defensive chemical weapon that will scare any potential predator who dares to bite this part.

[4] The gills and the rhinophores are retractile in internal sheaths and their basis has a purple margin.