A New York Police Department spokesman said the Australian-born actor had an appointment for a massage at the Manhattan apartment, which is believed to be his home. The housekeeper who went to let him know the masseuse had arrived found him lying facedown at the foot of his bed. He was later pronounced dead.
Ledger was nominated for an Oscar for Ang Lee's Brokeback Mountain, on the sets of which he met his wife, actor Michelle Williams. Ledger and Williams lived in Brooklyn and had a daughter Matilda until they split up in 2007.
Ledger starred in A Knight's Tale, The Patriot, and Monster's Ball and was to appear as the Joker in The Dark Knight, a sequel to 2005's Batman Begins.
NYPD sources are reported to have said sleeping pills were found at the scene, but no suicide note.