F for Fake (French: Vérités et mensonges, "Truths and lies") is a 1973 docudrama film co-written, directed by, and starring Orson Welles who worked on the film alongside François Reichenbach, Oja Kodar, and Gary Graver. The film focuses on Elmyr de Hory's recounting of his career as a professional art forger; de Hory's story serves as the backdrop for a meandering investigation of the natures of authorship and authenticity, as well as the basis of the value of art. Far from serving as a traditional documentary on de Hory, the film also incorporates Welles's companion Oja Kodar, hoax biographer Clifford Irving, and Orson Welles as himself. F for Fake is sometimes considered an example of a film essay.

In addition to the 88-minute film, in 1976, Welles also shot and edited a self-contained nine-minute short film as a "trailer", almost entirely composed of original material not found in the main film itself.

After performing magic tricks to children and quoting Jean Eugène Robert-Houdin to the effect that a magician is just an actor, Orson Welles makes a promise that everything seen in the next hour of the film will be factual. He is watched on by Oja Kodor, who partakes in an experiment in girl-watching, walking around deliberately drawing attention to herself and seeing how many men ogle her. Welles goes on to narrate the story of Elmyr de Hory, an art forger who sold many fake paintings to museums and collectors all over the world. De Hory throws a dinner party at his home in Ibiza, where he is feted by European society; one of his guests is Clifford Irving, who had published a biography of de Hory called Fake, and who tells about the art dealers who were fooled by De Hory's forgeries, leading Welles to consider whether this means art dealers and appraisers are fake also.

Welles notes the irony of Irving commenting on forgeries when he was revealed to have created a fake "authorized biography" of Howard Hughes, which contained unverified stories of Hughes' unusual behavior. Welles questions if believing such stories makes a person credulous or not, and questions the true wisdom of the experts who verified Irving's book as authentic. François Reichenbach tells how de Hory provided him with paintings of questionable authenticity, which art dealers seemed to willfully overlook. Welles recounts his own history with fakery: getting an acting job in Ireland by claiming to be a famous New York actor; his radio broadcast of The War of the Worlds; and how Citizen Kane was originally going to be a fictionalized version of Howard Hughes’ life.

Irving recounts how de Hory was destitute when younger and subsisted in America by making and selling forgeries, while avoiding the law through frequent relocations. He was offered his home in Ibiza by an art dealer, was never prosecuted as nobody witnessed the actual art forging, and his work revealed the depth of the art market's complicity in deceiving buyers. De Hory insists he never signed any forgery, leading Welles to question how much a signature truly matters on an art work, contrasting this point with the names of those who helped build the Chartres Cathedral are all unknown, but their work endures.

Finally, Welles recounts how Oja Kodar was spotted by Pablo Picasso while they were once holidaying in the same village, and he persuaded her to pose for him while he painted her. Picasso obliged when Kodar insisted she be allowed to keep the paintings, later becoming enraged after reading of an exhibition of his new works. He flew out to the exhibition to discover the pieces were all forgeries created by Kodar's grandfather. Kodar and Welles re-enect the exchange between Picasso and the grandfather, who defends his work with pride and suggests the forgeries go un-reported, to allow him an artistic legacy that Picasso already has. Picasso angrily demanded the paintings back, but the grandfather had burned them. Welles then confesses that he had promised everything in the "next hour" was true, and that hour had already passed, admitting the entire story of Kodar, her grandfather, and Picasso was made up. He apologizes, quotes Picasso's statement that art is a lie that makes us see the truth, and bids the audience good evening.

Orson Welles was hired to edit a documentary by François Reichenbach about the art forger Elmyr de Hory. The film grew over time to encompass de Hory, as well as de Hory's biographer Clifford Irving, who was revealed to be a forger himself. Keith Woodward explains: "following Irving’s hoax, Welles and his cinematographer, Gary Graver, shifted gears, scrambling to keep up with the Hughes affair, adding new shots, re-thinking the narrative, re-editing, re-combining different themes, incorporating emerging material." Welles used these circumstances to produce a meditation on the nature of fakery, which he called "a new kind of movie … it’s a form, in other words, the essay, the personal essay, as opposed to the documentary."

Several storylines are presented in the film, including those of de Hory, Irving, Welles, Howard Hughes and Kodar. About de Hory, we learn that he was a struggling artist who turned to forgery out of desperation, only to see the greater share of the profits from his deceptions go to doubly unscrupulous art dealers. As partial compensation for that injustice, he is maintained in a villa in Ibiza by one of his dealers. What is only hinted at in Welles's documentary is that de Hory had recently served a two-month sentence in a Spanish prison for homosexuality and consorting with criminals. (de Hory would commit suicide two years after the initial release of Welles's film, on hearing that Spain had agreed to turn him over to the French authorities.)