Trapania nebula is a species of sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Goniodorididae.

[2] This species was described from Madang, Papua New Guinea.

[3] This goniodorid nudibranch is translucent grey-brown with an irregular pattern of white covering most of the body.

The rhinophores and gills are edged with yellow or orange.

[3] Trapania nebula probably feeds on Entoprocta which often grow on sponges and other living substrata.