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. Many conspiracy fiction works also include the theme of secret history.