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.
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 single source for the notion that Vikings used A. muscaria to produce their berserker rages was first suggested by the Swedish professor Samuel Ödman in 1784. Ödman based his theories on reports about the use of fly agaric among Siberian shamans. The notion has become widespread since the 19th century, but no contemporary sources mention this use or anything similar in their description of berserkers. Today, it is generally considered an urban legend or at best speculation that cannot be proven. Muscimol is generally a mild relaxant, but could create a range of reactions within a range of people. It is possible that it could make a person incredibly angry, as well as make them "very jolly or sad, jump about, dance, sing or give way to great fright".
The red-and-white spotted toadstool is a common image in many aspects of popular culture, especially in children's books, film, garden ornaments, greeting cards, and more recently computer games. Garden ornaments, and children's picture books depicting gnomes and fairies, such as the Smurfs, very often show fly agarics used as seats, or homes. Fly agarics have been featured in paintings since the Renaissance, albeit in a subtle manner. In the Victorian era they became more visible, even becoming the main topic of some fairy paintings.