Late Australian actor Heath Ledger, who played the Joker in "The Dark Knight", won the Oscar for best supporting actor at the 81st Academy Awards held in Hollywood's Kodak Theatre.

Ledger's father Kim, mother Sally and sister Kate accepted the award on his behalf, receiving a standing ovation as they walked onstage.

"Firstly, we'd like to thank the Academy for recognizing our son's amazing work," Kim Ledger said, "(we thank) Warner Brothers, and (director) Christopher Nolan in particular, for allowing Heath the creative license to develop and explore this crazy Joker character. To Steve Alexander, Heath's mentor, special friend and agent for 10 years. We love you Steve."

Ledger, who died of an accidental overdose of prescription medication on Jan. 22, 2008, has already posthumously won the Golden Globe and Screen Actors' Guild awards for his role as a mentally tortured Joker in the Batman sequel.

He is only the second person ever to win a posthumous Academy Award. Peter Finch won an Oscar for the 1976 film "Network" just months after his death.

Ledger's Oscar is expected to be held in trust for his three-year-old daughter Matilda, who will inherit the statuette when she turns 18.

"Heath, we both knew what you had created in the Joker was extraordinarily special, and had even talked about being here on this very day," said his sister, Kate.

(Xinhua New Agency February 23, 2009)