Omphalotus is a genus of basidiomycete mushroom, in the family Omphalotaceae, formally circumscribed by Victor Fayod in 1889.

Rolf Singer placed it and the related Lampteromyces in the Boletales due to the presence of the pigment variegatic acid.

[6] Since then, the genera have been found to have a close relationship with the genus Nothopanus, and the whole group to lie within the agaric family Marasmiaceae.

[5] Many members of the genus are known to be toxic, with consumption leading to gastrointestinal symptoms of nausea, vomiting and at times diarrhea.

[10] The toxic ingredient is a sesquiterpene compound known as illudin S.[11][12][13] The genus has a cosmopolitan distribution, found in forests around the world.