Apt Pupil is a 1998 American thriller film directed by Bryan Singer and starring Ian McKellen and Brad Renfro. It is based on the 1982 novella Apt Pupil by Stephen King. In the 1980s in southern California, high school student Todd Bowden (Renfro) discovers fugitive Nazi war criminal Kurt Dussander (McKellen) living in his neighborhood under the pseudonym Arthur Denker. Bowden, obsessed with Nazism and acts of the Holocaust, persuades Dussander to share his stories, and their relationship stirs malice in each of them.

The novella was first published in King's 1982 collection Different Seasons. Producer Richard Kobritz sought to adapt the novella into a film during the 1980s, but two actors he invited to play Dussander died. When filming began in 1987, a loss of financing led to the production being shut down. Forty minutes of usable footage existed, but production was never revived. In 1995, when rights to the novella returned to King, Bryan Singer petitioned the author for an opportunity to adapt the novella. With King's support, Singer filmed Apt Pupil with McKellen and Renfro in Altadena, California, in 1997. The director shortened the novella's storyline, reduced its violence, and changed the ending. Singer called Apt Pupil "a study in cruelty" with Nazism only serving as a vehicle for the capacity of evil.

During the $14 million production, a lawsuit was filed by several extras, including some underage who alleged that they were told to strip naked during a shower scene. There was no cause to file criminal charges, and a civil-case lawsuit was dismissed due to insufficient evidence. The film was released in the United States and Canada in October 1998 to mixed reviews and made under $9 million. The main actors won several minor awards for their performances.