Believer is a 2018 South Korean action crime film directed by Lee Hae-young. It is a remake of the 2012 Johnnie To film Drug War. The film features actor Kim Joo-hyuk's final film performance. The film was released in South Korea on May 22, 2018. An extended version was released theatrically on July 18, 2018.

Kim Joo-hyuk was a South Korean actor. He was known for his leading roles in the films My Wife Got Married (2008), The Servant (2010), and Yourself and Yours (2016), his supporting roles in Confidential Assignment (2017) and Believer (2018), as well as the television series Lovers in Prague (2005), God of War (2012), Hur Jun, The Original Story (2013) and Argon (2017). He was also an original regular cast member on the third season of the KBS2's reality-variety show 2 Days & 1 Night.