The Departed is a 2006 crime thriller film directed by Martin Scorsese and written by William Monahan. It is both an English-language remake of the 2002 Hong Kong film Infernal Affairs, and also loosely based on the real-life Boston Winter Hill Gang; the character Colin Sullivan is based on the corrupt FBI agent John Connolly, while the character Frank Costello is based on Irish-American gangster and crime boss Whitey Bulger. The film stars Leonardo DiCaprio, Matt Damon, Jack Nicholson, and Mark Wahlberg, with Martin Sheen, Ray Winstone, Vera Farmiga, Alec Baldwin, Anthony Anderson and James Badge Dale in supporting roles.

The film takes place in Boston and the surrounding metro area, primarily in the South Boston neighborhood. Irish Mob boss Frank Costello (Nicholson) plants Colin Sullivan (Damon) as a spy within the Massachusetts State Police; simultaneously, the police assign undercover state trooper Billy Costigan (DiCaprio) to infiltrate Costello's mob crew. When both sides realize the situation, Sullivan and Costigan each attempt to discover the other's identity before they are found out.

The Departed was a critical and commercial success, grossing $291.5 million on a budget of around $90 million and receiving acclaim for its direction, performances (particularly of DiCaprio, Nicholson, and Wahlberg), screenplay, and editing.

It won several accolades, including four Oscars at the 79th Academy Awards: for Best Picture, Best Director for Scorsese (his only personal Oscar win to date), Best Adapted Screenplay for Monahan, and Best Film Editing for editor Thelma Schoonmaker. The film also received six nominations each at the 64th Golden Globe Awards (winning one) and the 60th British Academy Film Awards, and two nominations at the 13th Screen Actors Guild Awards.