Psilocybe cyanescens (sometimes referred to as wavy caps or as the potent Psilocybe) is a species of potent psychedelic mushroom. The main compounds responsible for its psychedelic effects are psilocybin and psilocin. It belongs to the family Hymenogastraceae. A formal description of the species was published by Elsie Wakefield in 1946 in the Transactions of the British Mycological Society, based on a specimen she had recently collected at Kew Gardens. She had begun collecting the species as early as 1910.The mushroom is not generally regarded as being physically dangerous to adults. Since all the psychoactive compounds in P. cyanescens are water-soluble, the fruiting bodies can be rendered non-psychoactive through parboiling, allowing their culinary use. However, since most people find them overly bitter and they are too small to have great nutritive value, this is not frequently done.
Psilocybe cyanescens can sometimes fruit in colossal quantity; more than 100,000 mushrooms were found growing in a single patch at a racetrack in England.