The Westboro Baptist Church in Topeka, Kansas, says it will protest against any memorial held for Ledger in the United States because the 28-year-old actor supported homosexuals.
"I'm going to picket him in two places," parishioner Shirley Phelps told Sydney radio station 2Day FM.
"I'm going to stand outside of any public memorial service that he has here.
"And then the other place I'm going to picket him is when they prop him up to worship his dead, rotting carcass further at the Oscars. I'll be right outside by the red carpet."
It is understood Ledger's body will be returned to Perth, where his former school has offered to hold a memorial service.
The church has ruled out travelling to Australia for the funeral.
Good, if those ****ers come here I will personally fly interstate and shoot them in the head myself.