Ceratosoma tenue is a species of colourful dorid nudibranch, a sea slug, a shell-less marine gastropod mollusc in the family Chromodorididae.

[2] This sea slug is widespread throughout the tropical waters of the Indo-Pacific area, from the oriental African coast to Hawaii.

[3] Ceratosoma tenue can grow to a maximal size of 12 centimetres (4.7 in) length.

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

Another specificity of many species of Ceratosoma 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.