The Mushroom coral reticulidia (Reticulidia fungia) is a species of sea slug, a dorid nudibranch, a shell-less marine gastropod mollusk in the family Phyllidiidae.

[1][2] Reticulidia fungia grows to a maximum length of 40 mm.

The base of these ridges have a fine, white border.

The mantle margin is broad and blue-grey in colour.

It has a single, black line around the side of its foot occurring slightly above its gills.