Amanita muscaria, commonly known as the fly agaric or fly Amanita , is a poisonous and psychoactive basidiomycete fungus, one of many in the genus Amanita. Native throughout the temperate and boreal regions of the Northern Hemisphere, Amanita muscaria has been unintentionally introduced to many countries in the Southern Hemisphere, generally as a symbiont with pine plantations, and is now a true cosmopolitan species. It associates with various deciduous and coniferous trees. The quintessential toadstool, it is a large white-gilled, white-spotted, usually deep red mushroom, one of the most recognizable and widely encountered in popular culture. Several subspecies, with differing cap colour, have been recognised to date, including the brown regalis (considered a separate species), the yellow-orange flavivolvata, guessowii, and formosa, and the pinkish persicina. Genetic studies published in 2006 and 2008 show several sharply delineated clades which may represent separate species.
Although generally considered poisonous, deaths are extremely rare, and it has been consumed as a food in parts of Europe, Asia, and North America after parboiling in water. Amanita muscaria is now primarily famed for its hallucinogenic properties, with its main psychoactive constituent being the compound muscimol. It was used as an intoxicant and entheogen by the peoples of Siberia and has a religious significance in these cultures. There has been much speculation on traditional use of this mushroom as an intoxicant in places other than Siberia; however, such traditions are far less well-documented.
A large conspicuous mushroom, Amanita muscaria is generally common and numerous where it grows, and is often found in groups with basidiocarps in all stages of development. Fly agaric fruiting bodies emerge from the soil looking like a white egg, covered in the white warty material of the universal veil. Dissecting the mushroom at this stage will reveal a characteristic yellowish layer of skin under the veil which assists in identification. As the fungus grows, the red color appears through the broken veil and the warts become less prominent; they do not change in size but are reduced relative to the expanding skin area. The cap changes from globose to hemispherical, and finally to plate-like and flat in mature specimens. Fully grown, the bright red cap is usually around 8–20 cm (3–8 in) in diameter, although larger specimens have been found. The red color may fade after rain and in older mushrooms. After emerging from the ground, the cap is covered with numerous small white to yellow pyramid-shaped warts. These are remnants of the universal veil, a membrane that encloses the entire mushroom when it is still very young. The free gills are white, as is the spore print. The oval spores measure 9–13 by 6.5–9 μm, and are non-amyloid, that is, they do not turn blue with the application of iodine. The stipe is white, 5–20 cm high (2–8 in) by 1–2 cm (0.4–0.8 in) wide, and has the slightly brittle, fibrous texture typical of many large mushrooms. At the base is a bulb that bears universal veil remnants in the form of two to four distinct rings or ruffs. Between the basal universal veil remnants and gills are remnants of the partial veil (which covers the gills during development) in the form of a white ring. It can be quite wide and flaccid with age. There is generally no associated smell other than a mild earthiness.
Although very distinctive in appearance, the fly agaric has been mistaken for other yellow to red species in the Americas, including Armillaria cf. mellea and the edible Amanita basii—a Mexican species similar to A. caesarea of Europe. Poison control centers in the U.S. and Canada are aware that amarill is a common name for A. caesarea-like species in Mexico, not just the Spanish for 'yellow'. Amanita caesarea can be distinguished as it has an entirely orange to red cap, lacking the numerous white warty spots of the fly agaric. Furthermore the stem, gills and ring are bright yellow, not white. Finally the volva is a distinct white bag, not broken into scales. In Australia, the introduced fly agaric may be confused with the native vermilion grisette (Amanita xanthocephala), which grows in association with eucalypts. The latter species generally lacks the white warts of Amanita muscaria and bears no ring.
Amanita muscaria is a cosmopolitan mushroom, native to conifer and deciduous woodlands throughout the temperate and boreal regions of the Northern Hemisphere, including high elevations of warmer latitudes in regions like the Hindu Kush, the Mediterranean and Central America. A recent molecular study proposes an ancestral origin in the Siberian–Beringian region in the Tertiary period before radiating outwards across Asia, Europe and North America. Though generally encountered in autumn, the season can vary in different climates: fruiting occurs in summer and autumn across most of North America, but later in autumn and early winter on the Pacific coast. It is often found in similar locations to Boletus edulis, and may appear in fairy rings. Conveyed with pine seedlings, it has been widely transported into the southern hemisphere, including Australia, New Zealand, South Africa and South America.
Ectomycorrhizal, Amanita muscaria forms symbiotic relationships with a wide variety of trees, including pine, spruce, fir, birch, and cedar. Commonly seen under introduced trees, Amanita muscaria is the fungal equivalent of a weed in New Zealand, Tasmania and Victoria, forming new associations with southern beech (Nothofagus). It is also invading native rainforest in Australia, where it may be displacing native species. Furthermore, it appears to be spreading northwards, with recent reports placing it near Port Macquarie on the New South Wales north coast. Although it has not spread to eucalypts in Australia, it has been recorded associating with them in Portugal.
Amanita muscaria poisoning typically occurs in either young children or people ingesting it for a hallucinogenic experience. Occasionally, immature button forms have been mistaken for edible puffballs. Additionally, the white spots may be washed away during heavy rain and it can then appear similar to the edible Amanita caesarea.
Amanita muscaria contains a number of biologically active agents, at least two of which, muscimol and ibotenic acid, are known to be psychoactive. A toxic dose in adults is approximately 6 mg muscimol or 30 to 60 mg ibotenic acid; this is typically about the amount found in one cap of Amanita muscaria. However, the amount and ratio of chemical compounds per mushroom varies widely from region to region and season to season, which further confuses the issue. Spring and summer mushrooms have been reported to contain up to 10 times as much ibotenic acid and muscimol compared to autumn fruitings.
A fatal dose has been calculated at approximately 15 caps. Deaths from Amanita muscaria have been reported in historical journal articles and newspaper reports; however, with modern medical treatment a fatal outcome would be extremely rare. Many older books mistakenly list it as deadly, giving the impression that it is far more toxic than it really is. The North American Mycological Association has stated there are no reliably documented fatalities in the past 100 years. The vast majority (90% or more) of mushroom poisoning deaths are from having eaten either the greenish to yellowish death cap (Amanita phalloides) or one of the several white Amanita species known as destroying angels. The active constituents of this species are water soluble, and boiling and then discarding the cooking water will at least partly detoxify Amanita muscaria. However, drying may increase potency as the process facilitates the conversion of ibotenic acid to the more potent muscimol. According to some sources, once detoxified, the mushroom becomes edible.

Plodno tijelo je građeno od stručka i klobuka; stručak je bijele boje i zadebljan na dnu, dok je klobuk na vrku žarko crvene boje i ima brojne bijele ljuske.
Raste u Europi, Americi i Africi od juna do kasne jeseni u brezovim, ali i mješovitim šumama, na sunčanim proplancima.
Mada otrovna, smatra se da u sjevernoj Europi, kao i u dijelovima Rusije raste varijacija koja je jestiva, ali joj je crvena kora mora oguliti. Također se smatra da sa oguljenom korom sa klobuka i prokuhana u vrućoj vodi oko deset minuta, jestivom i u južnoj Europi. Pravilo važi za mlađe primjerke, jer kod starijih gljiva otrov prelazi u meso.