This paper explores the pragmatic foundations of unreliable narration (UN), a narrative technique highly popular in western literary texts. It sets out by giving a critique of the competing theoretic frameworks of UN, namely the seminal Boothian concept and more recent constructivist approaches. It is argued that both frameworks neglect a pragmatic perspective as the most viable way for identifying and analysing UN. Such a pragmatic model is then developed on the basis of theories of cooperation, such as the Gricean maxims, relevance theory, and politeness. The emerging definition of UN treats a narrator as unreliable if he or she violates the cooperative principle without intending an implicature. This model is tested against three prototypical UNs: Christie's The Murder of Roger Ackroyd, Ishiguro's The Remains of the Day, and Poe's The Tell-Tale Heart. These sample analyses yield a typology of UN: while pragmatic deviation is shown to be the intrinsic feature of the phenomenon, unreliable narrators vary according to their degree of intentionality. Finally, two recurring issues in the UN debate are briefly discussed: the existence of textual clues of UN, and the role of the reader in constructing unreliability.