We're wise to your act; you have rules. But the Joker, he has no rules. No one is going to give him up for you. There's only one way to stop him and you know it. Just take off that mask of yours. Or are you gonna let some more people die while you make up your mind?
~ Sal Maroni challenging Batman
Salvatore Maroni is the most powerful crime boss in Gotham City, and a major antagonist of the 2008 movie The Dark Knight. He was a member of the Falcone crime family who takes over the family upon Falcone's incarceration. When Batman threatens his grip on Gotham's criminal underworld, Maroni partners with Gambol and The Chechen to decide what to do next. They ultimately decide to hire the Joker, setting the film's plot in motion.
He is portrayed by Eric Roberts who played The Master in the Doctor Who movie.
Sal was the only son of Luigi Maroni, Don of the Maroni crime family and grew up in the care of the Maroni family. The Maronis battled for control of Gotham with the ruling family, the Falcones. That changed once Luigi died and Sal inherited his mob and slowly rose to prominence in Gotham's underworld and take over it once Falcone met his end.
The Dark Knight
He forms an alliance with Chechen and Gambol to fight Batman and Harvey Dent. In a meeting with Gotham's underworld, Sal and his fellow mob bosses are confronted by the Joker, who himself offers to murder the Batman for half of all their money, but the mob refuses. They change their minds after Batman captures their accountant Lau in Hong Kong and delivers him to the Gotham police. Lau's testimony allows Dent to put all the mobsters in Gotham on trial, but as one of the bosses Maroni is able to make bail. Maroni is next seen when he is being interrogated by Batman above a club hours after the apparent murder of Lieutenant James Gordon. Despite Batman breaking one of his legs by throwing him off a building, Maroni does not disclose the Joker's whereabouts, instead lecturing Batman about letting people die by not turning himself in to the Joker. Later in the film after countless people and several city officials have been killed and Dent badly scarred because of the Joker, Maroni realizes that joining forces with the Joker has created more chaos than he can handle and he tells Gordon the Joker's location.
He is interrogated by a scarred Harvey/"Two-Face" later. Using his coin to determine Maroni's fate, Two-Face flips it over. For Maroni's luck, the coin lands on the unscarred side, leading Two-Face to spare him and call him a "fortunate man". However, when Two-Face flips over the coin again, it lands on the scarred side, leading Two-Face to shoot the driver of his limo, causing it to flip over. While Two-Face survives the accident, Maroni's status goes unspecified afterwards, but it's likely that he was killed in the accident because he wasn't wearing his seatbelt.
In the comics, Maroni is the one responsible for scarring Harvey Dent and causing him to become Two-Face.