Jacob the Liar (German: Jakob der Lügner) is a 1975 war drama film directed by Frank Beyer, adapted by Beyer and Jurek Becker from the latter's novel of the same title. Set in Nazi-occupied Poland during the Holocaust, the film centers on Jakob Heym (played by Vlastimil Brodský), a Polish Jew who attempts to raise the morale inside the ghetto by sharing encouraging rumors that he claims he has heard on an (imaginary) radio. The film was a co-production between East Germany and Czechoslovakia. It premiered on East German television on 22 December 1974, and was released theatrically on 18 April 1975.

Work on the picture began in 1965, but production was halted in summer 1966. Becker, who had originally planned Jacob the Liar as a screenplay, decided to make it a novel instead. In 1972, after the book garnered considerable success, work on the picture resumed. Jacob the Liar was both a critical and commercial success, earning multiple international accolades and becoming the first East German film to be entered into the Berlin International Film Festival, where it competed for the Golden Bear. The film was also nominated for Best Foreign-Language Film at the 49th Academy Awards, the only East German film to ever be nominated.

An English-language remake, starring Robin Williams, was released in 1999.