Nembrotha cristata is a species of colourful sea slug, a polycerid nudibranch, a marine gastropod mollusk in the family Polyceridae.

[2] This species of sea slug is black with green markings; adults are around 50 mm long, and they live on rock or coral reefs in the tropical Indo-West Pacific Ocean.

Nembrotha cristata is a large black nembrothine ("nembrothid" in much of the literature) growing to at least 50 mm long.

These sea slugs live on coral or rock reefs and have a lifespan of up to a year.

[4] The bright colours of this nudibranch species are an aposematic warning to predators.