- Christian Bale as Bruce Wayne / Batman:
- A billionaire socialite who, after witnessing his parents' death in a mugging at age 8, travels the world for seven years before returning home to operate as a bat-masked vigilante hailed as Gotham City's "Dark Knight", using fear against the city's criminal underworld at night. Bale said he was confident in his choice to return in the role because of the positive response to his portrayal in Batman Begins. He continued training in the Keysi Fighting Method and performed many of his own stunts, but did not gain as much muscle as in the previous film because the new Batsuit allowed him to move with greater agility. Bale described Batman's dilemma as whether "[his crusade is] something that has an end. Can he quit and have an ordinary life? The kind of manic intensity someone has to have to maintain the passion and the anger that they felt as a child, takes an effort after a while, to keep doing that. At some point, you have to exorcise your demons." He added, "Now you have not just a young man in pain attempting to find some kind of an answer, you have somebody who actually has power, who is burdened by that power, and is having to recognize the difference between attaining that power and holding on to it." Bale felt Batman's personality had been strongly established in the first film, so it was unlikely his character would be overshadowed by the villains, stating: "I have no problem with competing with someone else. And that's going to make a better movie."
- Michael Caine as Alfred Pennyworth:
- Bruce's trusted butler and confidant, who supplies useful advice to Bruce and likeness as a father figure, leading him to be labeled "Batman's batman".
- Heath Ledger as The Joker:
- A psychopathic illegalist mastermind portraying himself as an "agent of chaos", who rises from the criminal underworld by thrusting Gotham into anarchy and drawing Batman ever closer to crossing the fine line between heroism and vigilantism. Before Ledger was cast in July 2006, Paul Bettany, Lachy Hulme, Adrien Brody, Steve Carell, and Robin Williams publicly expressed interest in it. However, Nolan had wanted to work with Ledger on a number of projects in the past (including unsuccessfully approaching Ledger for the role of Batman in Batman Begins) and was agreeable to Ledger's chaotic interpretation of the character. When Ledger saw Batman Begins, he had realized a way to make the character work that was consistent with the film's tone: he described his Joker as a "psychopathic, mass murdering, schizophrenic clown with zero empathy". In the film, the Joker has a Glasgow smile, and his trademark chalk-white skin and red lips are makeup rather than the result of chemical bleaching, as in the traditional portrayal of the character. Throughout the film, the Joker states his desire to upset social order through crime, and comes to define himself by his conflict with Batman. To prepare for the role, Ledger lived alone in a hotel room for a month, formulating the character's posture, voice, and personality, and kept a diary, in which he recorded the Joker's thoughts and feelings. While he initially found it difficult, Ledger eventually generated a voice unlike Jack Nicholson's character in Tim Burton's 1989 Batman film. He was also given Batman: The Killing Joke and Arkham Asylum: A Serious House on Serious Earth, which he "really tried to read and put it down". Ledger also cited A Clockwork Orange and Sid Vicious as "a very early starting point for Christian [Bale] and I. But we kind of flew far away from that pretty quickly and into another world altogether." "There's a bit of everything in him. There's nothing that consistent", Ledger said, and added, "There are a few more surprises to him." Ledger was allowed to shoot and mostly direct the videos the Joker sends out as warnings. Each take Ledger made was different from the last. Nolan was impressed enough with the first video shoot that he chose to not be present when Ledger shot the video with a kidnapped reporter (Anthony Michael Hall). On January 22, 2008, after he had completed filming The Dark Knight, Ledger died of an accidental prescription drug overdose, leading to intense press attention and memorial tributes. "It was tremendously emotional, right when he passed, having to go back in and look at him every day [during editing]", Nolan recalled. "But the truth is, I feel very lucky to have something productive to do, to have a performance that he was very, very proud of, and that he had entrusted to me to finish." All of Ledger's scenes appear as he completed them in the filming; in editing the film, Nolan added no "digital effects" to alter Ledger's actual performance posthumously. Nolan has dedicated the film in part to Ledger's memory.
- Gary Oldman as James Gordon:
- A lieutenant in the Gotham City Police Department and one of the city's few honest police officers, who forms a tenuous, unofficial alliance with Batman and Dent and is given the position of Police Commissioner by the city's mayor following the recent commissioner's assassination. Oldman described his character as "incorruptible, virtuous, strong, heroic, but understated". Nolan explained, "The Long Halloween has a great, triangular relationship between Harvey Dent and Gordon and Batman, and that's something we very much drew from." Oldman added that "Gordon has a great deal of admiration for him at the end, but [Batman] is more than ever now the dark knight, the outsider. I'm intrigued now to see: If there is a third one, what he's going to do?" On the possibility of another sequel, he said that "returning to [the role] is not dependent on whether the role was bigger than the one before".
- Aaron Eckhart as Harvey Dent:
- The district attorney hailed as Gotham's "White Knight", whose campaign against the criminal underworld leaves half of his face disfigured, turning him into a murderer with a split-personality bent on revenge. Nolan and David S. Goyer had originally considered using Dent in Batman Begins, but they replaced him with the new character Rachel Dawes when they realized they "couldn't do him justice". Before Eckhart was cast in February 2007, Liev Schreiber, Josh Lucas, and Ryan Phillippe had expressed interest in the role, while Mark Ruffalo auditioned. Matt Damon stated that he was considered for the role, but could not accept due to scheduling conflicts. Hugh Jackman was also considered for the part. Nolan chose Eckhart, whom he had considered for the lead role in Memento, citing his "extraordinary" ability as an actor, his embodiment of "that kind of chiselled, American hero quality" projected by Robert Redford, and his subtextual "edge". Eckhart was "interested in good guys gone wrong", and had played corrupt men in films such as The Black Dahlia, Thank You for Smoking, and In the Company of Men. Whereas Dent is depicted as a crime boss in most characterizations, Nolan chose to portray him as a twisted vigilante to emphasize his role as Batman's counterpart. Eckhart explained, "[He] is still true to himself. He's a crime fighter, he's not killing good people. He's not a bad guy, not purely." For Dent, Eckhart "kept on thinking about the Kennedys", particularly Robert F. Kennedy, who was "idealistic, held a grudge and took on the Mob". He had his hair lightened and styled to make him appear more dashing. Nolan told Eckhart to not make Dent's criminal persona "jokey with slurping sounds or ticks".
- Maggie Gyllenhaal as Rachel Dawes:
- Gotham City's assistant district attorney and Bruce's childhood friend, who is one of the few people who knows Batman's true identity. Gyllenhaal took over the role from Katie Holmes, who played the part in Batman Begins. In August 2005, Holmes was reportedly planning to reprise the role, but she eventually turned it down to film Mad Money with Diane Keaton and Queen Latifah. By March 2007, Gyllenhaal was in "final talks" for the part. Gyllenhaal has acknowledged her character is a damsel in distress to an extent, but says Nolan sought ways to empower her character, so "Rachel's really clear about what's important to her and unwilling to compromise her morals, which made a nice change" from the many conflicted characters whom she has previously portrayed.
- Morgan Freeman as Lucius Fox:
- The recently promoted CEO of Wayne Enterprises who, now fully aware of his employer's double life, serves more directly as Bruce's armorer for the Batsuit in addition to his corporate duties.
Monique Gabriela Curnen and Ron Dean portray Anna Ramirez and Michael Wuertz respectively, corrupt detectives in Gordon's unit. Nestor Carbonell appears as Anthony Garcia, the mayor of Gotham. Ng Chin Han portrays Lau, a corrupt Chinese LSI Holdings accountant Triad boss. Eric Roberts plays Sal Maroni, an Italian mafia boss who takes over Carmine Falcone's mob, and Ritchie Coster portrays the Chechen, a Chechen mafia boss in charge of drug-trafficking for the mob. Anthony Michael Hall appears as Mike Engel, a Gotham Cable News reporter, and Keith Szarabajka portrays Gerard Stephens, a detective in Gordon's unit. Joshua Harto plays Coleman Reese, an M&A law accountant at Wayne Enterprises who deduces Bruce's persona of Batman from Fox and plans to reveal it to Gotham. Melinda McGraw appears as Barbara Gordon, Gordon's wife, while Nathan Gamble appears as James Gordon Jr., Gordon's ten-year-old son. Michael Jai White portrays Gambol, an African mafia boss in charge of illegal gambling and extortion for the mob. Colin McFarlane reprises his role as Gillian B. Loeb, the Police Commissioner of Gotham.
The film's supporting cast includes Nydia Rodriguez Terracina as Judge Janet Surrillo, and Tom "Tiny" Lister Jr. as a prison inmate on one of the bomb-rigged ferries. Vincenzo Nicoli played a crime boss in the meeting that had been held by the Joker and Lau. William Fichtner played the Gotham National Bank manager, and Cillian Murphy returns in a cameo as Jonathan Crane / Scarecrow, who is apprehended early on in the film by Batman.
Musician Dwight Yoakam was approached for the roles of either the manager or a corrupt cop, but he chose instead to focus on his album Dwight Sings Buck. United States Senator Patrick Leahy—a fan of Batman comics who was previously an extra in the 1997 film Batman & Robin and also was a guest voice actor on Batman: The Animated Series—appears as a guest at Bruce Wayne's party. Matt Skiba, co-lead vocalist and guitarist of the bands Alkaline Trio and Blink-182, made a small appearance in the film. David Dastmalchian appears as Thomas Schiff, a paranoid schizophrenic from Arkham Asylum who joins the Joker's gang, but gets captured and held at gunpoint by Dent after posing as an Honor Guard at Loeb's funeral alongside the Joker himself.