Goniodoris mercurialis is a species of sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Goniodorididae.
This species was first described from False Bay, South Africa. It is found on both sides of the Cape Peninsula.[1]
This goniodorid nudibranch is translucent tan in colour, with large areas of white surface pigment on the oral tentacles and the back and sides of the body.
Goniodoris mercurialis feeds on colonial ascidians.