Ledger had an appointment for a massage at the SoHo apartment that is believed to be the home of the "Brokeback Mountain" actor, an NYPD spokesman said. The massage therapist and a housekeeper found his body at about 3:30 p.m. Authorities say the two tried to revive him, but he was already dead.
"We are all deeply saddened and shocked by this accident," Ledger's publicist, Mara Buxbaum, said in a statement Tuesday night. "This is an extremely difficult time for his loved ones and we are asking the media to please respect the family's privacy and avoid speculation until the facts are known."
After the news broke, hundreds gathered outside the apartment building on an upscale Soho street. Paparazzi and gawkers turned out, and police put up barricades to control the crowd. Onlookers craned their necks as officers brought out a black bodybag on a gurney and put it into a medical examiner's office van.
An autopsy is planned for Wednesday.
Ledger was an award-winning actor who chose his roles carefully. He was nominated for an Oscar for his performance as a gay cowboy in "Brokeback Mountain." During filming, he met Michelle Williams, who played his wife in the film. The two had a daughter, now 2-year-old Matilda. They lived together in Brooklyn until they split up last year.
Though his leading man looks propelled him to early stardom in films like "10 Things I Hate About You" and "A Knight's Tale," his career took a notable turn toward dramatic and brooding roles with 2001's "Monster's Ball."
"I had such great hope for him," said Mel Gibson, who played Ledger's vengeful father in "The Patriot," in a statement. "He was just taking off and to lose his life at such a young age is a tragic loss."
In the Australian city of Perth, Australia where Ledger was born and raised, his father called the actor's death "tragic, untimely and accidental."
"He was (a) down-to-earth, generous, kind-hearted, life-loving, unselfish individual, extremely inspirational to many," Kim Ledger said, reading from a prepared statement. "Heath has touched so many people on so many different levels during his short life."
Ledger chose to live a bohemian life in Brooklyn, one of the borough's most famous residents. His most recent acting choices were arguably the boldest yet: He costarred in "I'm Not There," in which he played one of many incarnations of Bob Dylan - as did Cate Blanchett, whose performance in that film earned an Oscar nomination Tuesday for best supporting actress.
And in what may be his final finished performance, Ledger took the character of the Joker, a role first portrayed on the screen by Jack Nicholson. Ledger's version of the "Batman" villain, glimpsed in early teaser trailers, made it clear that his Joker would be more depraved and dark.
Ledger told The New York Times in a November interview that he "stressed out a little too much" during the Dylan film and had trouble sleeping while portraying the Joker, whom he called a "psychopathic, mass-murdering, schizophrenic clown with zero empathy."
"Last week I probably slept an average of two hours a night," Ledger told the newspaper. "I couldn't stop thinking. My body was exhausted, and my mind was still going." He said he took two Ambien pills, which worked for only an hour, the paper said.
Ledger was a widely recognized figure in his Manhattan neighborhood, where he used to shop at a home and children's store. Michelle Vella, an employee there, said she had frequently seen Ledger with his daughter - carrying the toddler on his shoulders, or having ice cream with her.
"It's so sad. They were really close," Vella said. "He's a very down-to-earth guy and an amazing father."
