Heath Ledger has been found dead in a Manhattan apartment at around 8.30pm UK time after a suspected drugs overdose.
The actor - who was nominated for an Oscar for his role in Brokeback Mountain - was 28 years old.
Australian Ledger was part way through shooting Terry Gilliam's The Imaginarium Of Doctor Parnassus and was in talks to make a film with Terrence Malick. He will appear as The Joker in upcoming Batman film The Dark Knight.
A police spokeswoman said that Ledger had been found by his housekeeper when she went to wake him for a massage appointment.
She added that they were investigating the possibility of an overdose and that pills were found near the bed.
Ledger split up with his fiancee Michelle Williams last September. He leaves his daughter with Williams, Matilda Rose, aged two.