Which Scorsese film is a remake of the 1997 Hong Kong film 'Infernal Affairs'?

The Scorsese film that remakes the Hong Kong crime thriller Infernal Affairs is The Departed. Released in 2006, it relocates the story from Hong Kong to Boston, where an undercover police officer infiltrates an Irish-American crime syndicate while a gang mole rises inside the Massachusetts State Police.

The film stars Leonardo DiCaprio as Billy Costigan, Matt Damon as Colin Sullivan, and Jack Nicholson as crime boss Frank Costello. William Monahan adapted the screenplay, reshaping the original's premise around Boston's criminal history and the real-life Winter Hill Gang. Martin Scorsese's version is therefore an adaptation and remake, not an entirely original plot.

A common mix-up is the year in the question: Infernal Affairs was released in 2002, not 1997. It became a trilogy, while The Departed mainly draws on the first film's central setup. The Departed won Scorsese his first Academy Award for Best Director and also won Best Picture.