The Fly Agaric (Amanita muscaria) is a distinctive gilled mushroom found in parts of North America, Europe, Asia, and elsewhere. The cap is covered with irregular, white warts, and, depending on age, weathering, and subspecies, the cap color ranges from bright red to orange to yellow to white (the Yellow-orange, or guessowii¹, subspecies is shown here).
Also note the bulbous base, the membranous ring on the upper stalk, and the white, free (meaning they're not attached to the stalk) gills -- three features shared by members of the genus Amanita. Though the genus contains some edible and medicinal species, many others are strictly toxic.
A Peterson's Field Guide² describes the Fly Agaric as "a well-known intoxicant, reported to produce sensual derangement, erratic behavior, delirium, deep 'death-like' sleep, and in some cases, death." Many other sources simply call this species poisonous.
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¹Many sources call this subspecies formosa.
²A Field Guide to Venomous Animals and Poisonous Plants (1998) by Steven Foster and Roger Caras, page 200.