In satire, truthiness is a "truth" that a person claims to know intuitively "from the gut" without regard to evidence, logic, intellectual examination, or facts.

American television comedian Stephen Colbert revealed this definition as the subject of a segment called "The Wørd" during the pilot episode of his political satire program The Colbert Report on October 17, 2005. By using this as part of his routine, Colbert satirized the misuse of appeal to emotion and "gut feeling" as a rhetorical device in contemporaneous socio-political discourse. He particularly applied it to U.S. President George W. Bush's nomination of Harriet Miers to the Supreme Court and the decision to invade Iraq in 2003. Colbert later ascribed truthiness to other institutions and organizations, including Wikipedia. Colbert has sometimes used a quasi-Latin version of the term, "Veritasiness".

Truthiness, although a "stunt word", was named Word of the Year for 2005 by the American Dialect Society and for 2006 by Merriam-Webster. However, linguist and OED consultant Benjamin Zimmer pointed out that the word truthiness already had a history in literature and appears in the Oxford English Dictionary (OED), as a derivation of truthy, and The Century Dictionary, both of which indicate it as rare or dialectal, and to be defined more straightforwardly as "truthfulness, faithfulness".