David Hicks, the Australian convicted of supporting terrorism by a US military court, has arrived home from Guantanamo Bay.
Hicks was taken directly to Yatala prison
He spent five years at the US detention centre in Cuba, and under a deal with prosecutors will serve only seven more months of a seven-year sentence.
He admitted training with al-Qaeda in Afghanistan in 2001, but denied any prior knowledge of the 9/11 attacks.
The 31-year-old will serve his sentence in Yatala prison near Adelaide.
A prison van was waiting for him at the air force base outside Adelaide where his plane landed at 0950 (0020 GMT).
He had been flown from Guantanamo Bay in a jet chartered by the Australian government, in the custody of Australian prison officers and police, accompanied by his lawyer.
The plane had to fly via Mexico as the United States refused to allow it to enter American airspace.
"Mr Hicks is now in the custody of the South Australian correctional services," said Australia's Attorney General Philip Ruddock.
"If people train with terrorist organisations, and that training to learn how to attack civilian populations ... we regard them as very serious issues," he said.
Hicks' imprisonment for five years without trial offended a basic sense of Australian fair play and the government of Prime Minister John Howard came under enormous public pressure to secure his release, says the BBC's Nick Bryant in Sydney.
But Foreign Minster Alexander Downer stressed that Hicks had been involved with a violent organisation.
"This is somebody who was not just passing through Afghanistan on a backpacker's holiday and happened to meet someone from al-Qaeda and just said g'day to him," Mr Downer said.
Hicks' lawyer said that his client was very happy to be back in Australia.
"He visibly was elated when we touched down," said David McLeod, who travelled with him.
Hicks' father, Terry, who has campaigned for his son's release, said that David would be "over the moon".
He added that he remained sceptical about his son's deal with the US authorities.
"As far as I'm concerned, he's been coerced into all this," said Terry Hicks.
David Hicks was arrested by US forces in Afghanistan in 2001 and spent five years at Guantanamo Bay, much of it without charge and in solitary confinement.
He eventually became the first inmate from the camp to be convicted of terror charges.
Many Australians disagree with the way Hicks has been treated
He pleaded guilty before a military commission in March to providing material support for terrorism.
He admitted he had very briefly fought Western troops in Afghanistan at the end of 2001, before selling his gun and trying to escape by taxi to neighbouring Pakistan.
Under the terms of his plea bargain, he was allowed to serve out the rest of his time in prison in Australia.
He will be held in a high-security wing at Yatala prison, where he is expected to have little contact with other prisoners.
His telephone calls will be monitored and he will only be allowed non-contact visits.
Hicks also agreed to withdraw claims that he had been mistreated at Guantanamo Bay and promised not to speak to the press for a year.
However, the attorney general said that such a ban appeared to be unenforceable under Australian law.
"We are of the view that he's free - once he has concluded his penal servitude - to speak as he wishes, but not to profit," said Mr Ruddock.
Under Australian law, convicted criminals cannot sell their stories to the media.