Aleister Crowley, born Edward Alexander Crowley, was a British occultist, writer, mountaineer, poet, and yogi. He was an influential member of several occult organizations, including the Golden Dawn, the A∴A∴, and Ordo Templi Orientis (O.T.O.), and is best known today for his occult writings, especially The Book of the Law, the central sacred text of Thelema. He gained much notoriety during his lifetime, and was dubbed "The Wickedest Man In the World."
Aleister Crowley died of a respiratory infection in a Hastings boarding house on 1 December 1947 at the age of 72.