In literature and film, an unreliable narrator (a term coined by Wayne C. Booth in his 1961 book The Rhetoric of Fiction ) is a literary device in which the credibility of the narrator is seriously compromised. This unreliability can be due to psychological instability, a powerful bias, a lack of knowledge, or even a deliberate attempt to deceive the reader or audience. Unreliable narrators are usually first-person narrators, but third-person narrators can also be unreliable.

The nature of the narrator is sometimes immediately clear. For instance, a story may open with the narrator making a plainly false or delusional claim or admitting to being severely mentally ill, or the story itself may have a frame in which the narrator appears as a character, with clues to his unreliability. A more common, and dramatic, use of the device delays the revelation until near the story's end. This twist ending forces the reader to reconsider their point of view and experience of the story. In many cases the narrator's unreliability is never fully revealed but only hinted at, leaving the reader to wonder how much the narrator should be trusted and how the story should be interpreted.

The literary device of the unreliable narrator should not be confused with other devices such as euphemism, hyperbole, irony, metaphor, pathetic fallacy, personification, sarcasm, or satire; it may, however, coexist with such devices, as in Bret Easton Ellis’ American Psycho, a satire whose narrator is unreliable (and thus not credible). Similarly, historical novels, speculative fiction, and clearly delineated dream sequences are generally not considered instances of unreliable narration, even though they describe events that did not or could not happen.

Some works suggest that all narrators are inherently unreliable due to self-interest, personal bias, or selective memory; "reliable narrators" would be "unreliable narrators without hints or clues of their very own unreliability".