F/X (also known as or subtitled Murder by Illusion) is a 1986 American action thriller film directed by Robert Mandel, written by Gregory Fleeman and Robert T. Megginson, and starring Bryan Brown, Brian Dennehy, Diane Venora, Cliff De Young, and Angela Bassett in her film debut. The film follows a special effects expert who is hired by the U.S. Department of Justice to stage the murder of a mobster about to enter the Witness Protection Program, but complications arise when he is targeted for murder himself; meanwhile, an NYPD detective becomes suspicious of the circumstances of the case.

The film was released to positive reviews from critics and was a box office success, earning $20.6 million on a $10 million budget. A sequel, F/X2: The Deadly Art of Illusion, was released in 1991. A spinoff television series, F/X: The Series, was produced from 1996 to 1998.