Infernal Affairs is a 2002 Hong Kong crime-thriller film directed by Andrew Lau and Alan Mak. It tells the story of a police officer who infiltrates the triads, and a police officer secretly working for the same gang. The Chinese title means "the non-stop way", a reference to Avici, the lowest level of hell in Buddhism. The English title is a word play combining the law enforcement term "internal affairs" with the adjective infernal. Due to its commercial and critical success, Infernal Affairs was followed by a prequel, Infernal Affairs II, and a sequel, Infernal Affairs III, both released in 2003, as well as a 2006 American remake by Martin Scorsese entitled The Departed.
Pre-release publicity for Infernal Affairs focused on its star-studded cast (Andy Lau, Tony Leung, Anthony Wong, Eric Tsang, Kelly Chen and Sammi Cheng), but it later received critical acclaim for its original plot and its concise and swift storytelling style. The film did exceptionally well in Hong Kong, where it was considered "a box office miracle" and heralded as a revival of Hong Kong cinema which at the time was considered to be direly lacking in creativity.
Miramax Films acquired the United States distribution rights of this film and gave it a limited U.S. theatrical release in 2004.
The Infernal Affairs series was then remade by Martin Scorsese in 2006 as The Departed, which went on to win the Academy Award for Best Picture.