Phestilla melanobrachia is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusk in the family Trinchesiidae.

[2] There are two known colour forms of Phestilla melanobrachia, black and orange.

[3] Both of these feed on corals in the family Dendrophylliidae [4] and have been found to be genetically identical.

[5] This species was described from the Philippines.

[1] It has been reported from Hong Kong and Japan to Malaysia and East to Australia.