Secret Agent 666: Aleister Crowley, British Intelligence and the Occult is a 2008 Aleister Crowley biography by historian Richard B. Spence. The study proposes that the English occultist Aleister Crowley undertook activities for British and other intelligence services, situating the argument within archival sources and period print materials. Feral House published the book in 2008. Spence, an American historian at University of Idaho, previously published work on espionage and revolutionary politics, including the peer reviewed article Secret Agent 666: Aleister Crowley and British Intelligence in America, 1914–1918 in 2000. That book surveys Crowley's First World War period in the United States with attention to propaganda, informant activity, and contacts with German and American actors.