Blue Owsley is a particular strain of psychedelic mushrooms that originated in the United States during the 1960s. It is also known by several other synonyms that include "blue meanies," "blue leggers," and "psilocybe caerulescens." These synonyms are used interchangeably to refer to the same species of psilocybin mushrooms. The active ingredient in Blue Owsley and other psilocybin mushrooms is psilocybin, which has a powerful hallucinogenic effect on the user. While the use of Blue Owsley and other psychedelic drugs is illegal in most countries, they have been used for spiritual and therapeutic purposes by certain cultures throughout history.