Omphalotus nidiformis, or ghost fungus, is a gilled basidiomycete mushroom found in southern Australia most notable for its bioluminescent properties. Generally found growing on dead or dying trees, it is saprotroph and parasite.
Its scientific name is derived from the Latin nidus "nest", hence 'nest shaped'. Similar in appearance to the oyster mushroom, it was previously considered a member of the same genus, Pleurotus, and described under the former names Pleurotus nidiformis or Pleurotus lampas. However, it is poisonous and while not lethal, consuming this mushroom leads to severe cramps and vomiting. Poisonings have occurred over confusion with oyster mushrooms. It is one of several species with bioluminescent properties occurring worldwide, all of which are poisonous with the exception of Armillaria.