Former SAS corporal Ben Roberts-Smith, who won Australia's highest military honour the Victoria Cross for his actions in Afghanistan, had sued three Nine Entertainment newspapers and their journalists over articles that accused him of killing unarmed Afghan civilians outside the rules of war.
But a Federal Court judge ruled on June 1 that the newspapers had proven most of their allegations.
Roberts-Smith filed an appeal on July 11, the court said in a website post, without providing any further details.
A lawyer for Roberts-Smith did not respond to a request from Reuters for comment.
Nine's managing director of publishing, James Chessell, said the company would oppose the appeal.
"We believe the Federal Court's judgment is comprehensive and categorical," Chessell said in a statement.
" We will always stand up for journalism that is in the public interest."
Roberts-Smith, who was not in court for the June 1 judgment, was quoted as saying on June 15 that he stood by his actions while serving in the military and disagreed with the outcome of his lawsuit.
"It's a terrible outcome and it's the incorrect outcome," he was quoted telling Nine's television arm.
"We will look at (the judgement) and consider whether or not we need to file an appeal," he said at the time.
(Reporting by Byron Kaye; editing by Robert Birsel)
By Byron Kaye
