Amanita muscaria, commonly known as the fly agaric or fly amanita, is a basidiomycete fungus of the genus Amanita. Its common name derives from its traditional use as an insecticide. It is a distinctive, large white-gilled mushroom typically featuring a bright red cap covered with white warts. The complex genetic diversity of A. muscaria suggests that it is a species complex. It is a widely distributed mushroom native to temperate and boreal forests of the Northern Hemisphere, now also naturalised in the Southern Hemisphere, forming symbiotic relationships with various trees and spreading invasively in some regions.
Ingestion of the mushroom can cause poisoning, especially in children and those seeking its hallucinogenic effects, due to psychoactive compounds like muscimol and the ibotenic acid; however, fatal poisonings are extremely rare. Parboiling reduces toxicity, though drying converts ibotenic acid into muscimol, retaining psychoactive effects. Some cultures use it as food after preparation. Indigenous peoples of Siberia used A. muscaria as an inebriant and entheogen. It has been controversially linked to Santa Claus, Viking berserkers, Vedic soma, and early Christianity, though evidence is sparse and disputed. Its rise in the 2020s as a legal hallucinogen alternative has led to Food and Drug Administration scrutiny.