Goniobranchus alderi is a species of colourful sea slug, a dorid nudibranch, a marine gastropod mollusc in the family Chromodorididae.

[4] Goniobranchus alderi has a pattern of red lines forming a loose reticulate network on the mantle.

The gills are white with red lines and the rhinophores have red clubs with small white spots.

An animal from Sagami Bay, Japan identified as Chromodoris tinctoria is a good match for the original illustration.

A 2020 study has shown that there are probably five species without names in this complex, with Goniobranchus sp.