Phyllodesmium longicirrum, common name the solar-powered phyllodesmium, is a species of sea slug, an aeolid nudibranch, a marine gastropod mollusc in the family Facelinidae.

[1] The distribution of Phyllodesmium longicirrum includes Australia and Indonesia.

[2] This is a very large species, growing to at least 140 mm.

Phyllodesmium longicirrum contains photosynthetic zooxanthellae, which allow it to draw energy from sunlight, hence its common name, the solar-powered phyllodesmium.

[4][5] Phyllodesmium longicirrum feeds on soft coral Sarcophyton trocheliophorum (family Alcyoniidae).