Trapania armilla is a species of sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Goniodorididae.
This species was first described from Bali, Indonesia.
[2] This goniodorid nudibranch is opaque white in colour, with a thin brown ring halfway along the oral tentacles.
The gills are unusually large for a Trapania and the body is covered with raised irregular bumps.
Trapania armilla probably feeds on Entoprocta, which often grow on sponges and other living substrata.