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

It occurs in the tropical Western Pacific Ocean from Australia to the Philippines[4] and rarely as far East as the Marshall Islands.

[5] Goniobranchus coi has a white body and foot, but is instantly recognizable by its distinct dorsal pattern.

The gills and rhinophores range in colour between different individuals from translucent white, through pale-yellow and light-brown.

[6][7][8] Like most sea slugs in the superfamily Doridoidea, Goniobranchus coi feeds on sponges.