The conspiracy thriller (or paranoid thriller) is a subgenre of thriller fiction. The protagonists of conspiracy thrillers are often journalists or amateur investigators who find themselves (often inadvertently) pulling on a small thread which unravels a vast conspiracy that ultimately goes "all the way to the top." The complexities of historical fact are recast as a morality play in which bad people cause bad events, and good people identify and defeat them. Conspiracies are often played out as "man-in-peril" (or "woman-in-peril") stories, or yield quest narratives similar to those found in whodunnits and detective stories.
A common theme in such works is that characters uncovering the conspiracy encounter difficulty ascertaining the truth amid the deceptions: rumors, lies, propaganda, and counter-propaganda build upon one another until what is conspiracy and what is coincidence become entangled.
A considerable part of the Conspiracy fiction works can also be considered as being secret history.
John Buchan's 1915 novel The Thirty-Nine Steps weaves elements of conspiracy and man-on-the-run archetypes. Graham Greene's 1943 novel Ministry of Fear (brought to the big screen by Fritz Lang in 1944) combines all the ingredients of paranoia and conspiracy familiar to aficionados of the 1970s thrillers, with additional urgency and depth added by its wartime backdrop. Greene himself credited Michael Innes as the inspiration for his "entertainment".
Conspiracy fiction in the US reached its zenith in the 1960s and 1970s in the wake of a number of high-profile scandals and controversies, most notably the Vietnam War, the assassinations of John F. Kennedy, Robert Kennedy, and Martin Luther King Jr., as well as the Watergate scandal and the subsequent resignation of Richard Nixon from the presidency. Several fictional works explored the clandestine machinations and conspiracies beneath the orderly fabric of political life. American novelist Richard Condon wrote a number of conspiracy thrillers, including the seminal The Manchurian Candidate (1959), and Winter Kills, which was made into a film by William Richert in 1979. Illuminatus! (1969–1971), a trilogy by Robert Shea and Robert Anton Wilson, is regarded by many as the definitive work of 20th-century conspiracy fiction. Set in the late '60s, it is a psychedelic tale which fuses mystery, science fiction, horror, and comedy in its exhibition (and mourning, and mocking) of one of the more paranoid periods of recent history. Thomas Pynchon's The Crying of Lot 49 (1966) includes a secretive conflict between cartels dating back to the Middle Ages. Gravity's Rainbow also draws heavily on conspiracy theory in describing the motives and operations of the Phoebus cartel as well as the development of ballistic missiles during World War II. Inherent Vice also involves an intentionally ambiguous conspiracy involving a group known as the Golden Fang.
Umberto Eco's Foucault's Pendulum (1988) features a story in which the staff of a publishing firm, intending to create a series of popular occult books, invent their own occult conspiracy, over which they lose control as it begins to supplant the truth. The popular 2003 novel The Da Vinci Code by Dan Brown draws on conspiracy theories involving the Roman Catholic Church, Opus Dei and the Priory of Sion. Other contemporary authors who have used elements of conspiracy theory in their work include Margaret Atwood, William S. Burroughs, Don DeLillo, James Ellroy, Joseph Heller, Robert Ludlum, David Morrell and James Clancy Phelan.
One of the first science fiction novels to deal with a full-blown conspiracy theory was Eric Frank Russell's Dreadful Sanctuary (1948). This deals with a number of sabotaged space missions and the apparent discovery that Earth is being quarantined by aliens from other planets of the Solar System. However, as the novel progresses it emerges that this view is a paranoid delusion perpetuated by a small but powerful secret society. Philip K. Dick wrote a large number of short stories where vast conspiracies were employed (usually by an oppressive government or other hostile powers) to keep common people under control or enforce a given agenda. Other popular science fiction writers whose work features conspiracy theories include William Gibson, John Twelve Hawks, and Neal Stephenson.
Film and television 
One of the earliest exercises in cinematic paranoia was John Frankenheimer's The Manchurian Candidate. Its story of brainwashing and political assassination holds the distinction of not merely reflecting contemporary fears and anxieties, but anticipating future conspiracies and scandals by some years.
The screenplays for two of the best-known conspiracy thrillers were written by the same writer, Lorenzo Semple, Jr.: The Parallax View, directed by Alan J. Pakula, was released in 1974, while Sydney Pollack's Three Days Of The Condor entered release the following year. Pakula's movie is considered to be the second installment of a "paranoia trilogy," beginning with Klute (1971) and ending with All The President's Men (1976). Pakula returned to the theme with The Pelican Brief. Actor-producer Robert Redford played a part in 'Three Days of the Condor and All The President's Men. Director Costa-Gavras attributed two entries to the subgenre: Z and Missing.
On television, The X-Files was rich in conspiracy theory lore, often drawing influence from the aforementioned 1970s conspiracy thrillers.
Several Coen Brothers films focus on conspiracies. These include Burn After Reading, The Big Lebowski and The Man Who Wasn't There amongst others.
The role-playing game and card game GURPS Illuminati by Steve Jackson Games features a humorous look at conspiracy theories. The illuminated pyramid is the company's logo. Computer and videogames revolving around conspiracy include first-person shooter Deus Ex, adventure game Broken Sword, the neo-noir Max Payne series, stealth-action franchise Metal Gear Solid, the action-horror series Dead Rising and the historical action-adventure game series Assassin's Creed.
See also 
- Assassinations in fiction
- Illuminati in popular culture
- Secret societies in popular culture
- Spy fiction
- Dargis, Manohla (2005-02-07). "We're Sorry". The New York Times. Retrieved 2010-04-30.
- SF Books of the Damned
- Melley, Timothy (2000). Empire of Conspiracy: The Culture of Paranoia in Postwar America. Cornell University Press. ISBN 0-8014-3668-0.
- Didion, Joan (1990) . The White Album. Farrar, Straus and Giroux. ISBN 0-374-52221-9.
- Stylus Magazine: "Paranoid Time - The Conspiracy Thrillers of the 1970s"
- Book Review: Projecting Paranoia: Conspiratorial Visions in American Film
- ConspiracyFiction.com - short stories and weird theories in the conspiracyfic genre
- British TV Conspiracy Drama at the BFI's Screenonline