A {{thriller}} centered on the conflict between TheProtagonist and TheConspiracy, often with an elaborate ConspiracyTheory as the background.

The story starts off with either a minor meaningless crime or a high-profile murder. A person related to the criminal blamed or the uncovered victim notices some odd discrepancies in the official story and digs deeper. Before the protagonist realizes it, he/she/it are caught in a multi-layered plot that involves possibly EVERYONE, especially those [[ProperlyParanoid who are tasked with the official investigation]]... meaning that the hero/heroine can't go to the cops... or the press... or that janitor in the hallway they just passed who looks a little too much like the guy who'd been shadowing them the last day or so...

See also [[SoYouWantTo/WriteAConspiracyTheory So You Want To: Write A Conspiracy Theory]], for those interested in writing their own Conspiracy Thriller.
!!Examples of conspiracy thrillers include:

* Film/AllThePresidentsMen: Practically the TropeCodifier. Making it worse is that [[TruthInTelevision it really happened]]: [[ScandalGate Watergate]].
* VideoGame/AlphaProtocol
* Film/CapricornOne
* Film/CaptainAmericaTheWinterSoldier
* Film/ConspiracyTheory
* Literature/TheDaVinciCode
* VideoGame/DeusEx
* Series/EdgeOfDarkness
* Film/EnemyOfTheState
* HiddenAgenda
* TheManchurianCandidate
* ''Literature/MrBlank''
* Film/TheParallaxView
* Literature/SevenDaysInMay
* Film/ThreeDaysOfTheCondor
* Series/{{Utopia}}
* Series/PersonOfInterest has significant elements of this with regard to the government protecting [[SinisterSurveilance The Machine]]. From the perspective of several persons of interest it is explicitly this.