Amanda Knox said tonight she was "tremendously relieved and grateful" that Italy's highest court overturned her murder conviction for the murder of her room-mate.
American Ms Knox, 27, said in a statement that knowing she was innocent gave her "strength in the darkest times of this ordeal". She said she was buoyed by her family and friends and thanked her supporters.
In 2011 an appeal court cleared Ms Knox, of Seattle, of the 2007 murder of British student Meredith Kercher, 21, in Perugia, Italy, and ordered her release after she had spent four years in prison.
But her acquittal was overturned and she was convicted in absentia in 2014. Tonight Italy's highest court overturned that murder conviction, finally closing Ms Knox's long legal saga.
In a separate statement, Ms Knox's family expressed their "profound gratitude" to people who helped her.
"Finished!" Ms Knox's lawyer Carlo Dalla Vedova exulted after the decision was read out. "It couldn't be better than this."
The decision by the supreme Court of Cassation is the final ruling in the case, ending the long legal battle waged by Ms Knox and Italian co-defendant Raffaele Sollecito.
Both Ms Knox, who was awaiting the verdict in her home town, and Mr Sollecito have long maintained their innocence in the death of Ms Kercher, from Coulsdon, Surrey.
The supreme Court of Cassation overturned last year's convictions by a Florence appeal court, and declined to order another trial.
The decision means the judges, after thoroughly examining the case, concluded that a conviction could not be supported by the evidence.
Their reasoning will be released within 90 days.
The case has aroused strong interest in three countries for its explosive mix of young love, murder and flip-flop decisions by Italian courts.
Ms Kercher was found dead on November 2 2007, in the flat that she shared with Ms Knox and two other students. Her throat was slashed and she had been sexually assaulted.
Ms Knox and Mr Sollecito were arrested a few days later. Eventually another man, Rudy Guede from Ivory Coast, was arrested, tried and convicted of the murder in a separate trial and is serving a 16-year sentence.
The couple maintained their innocence, insisting that they had spent the evening together at Mr Sollecito's home watching a film, smoking marijuana and making love.
Ms Knox and Mr Sollecito were initially convicted by a Perugia court in 2009, then acquitted and freed in 2011, and then convicted again in 2014 in Florence after the supreme court overturned the acquittals and ordered a new appeal trial.
That Florence appeal conviction was overturned today.
Kercher family lawyer Francesco Maresca was clearly disappointed by the ruling.
"I think that it's a defeat for the Italian justice system," he said.
But across the Atlantic, a spontaneous shout of joy erupted from inside the Seattle home of Ms Knox's mother as the verdict was announced. Several relatives and supporters filtered into the garden, where they hugged and cheered.
Dalla Vedova said he called Knox to tell her the news, but she could not speak through her tears.
"She was crying because she was so happy," he said.
Mr Sollecito's lawyer, Luca Maori, called the young man with the good news from the steps of the court.
"You have your whole life ahead of you now, Raf" he told him.
Speaking to reporters, he added: "He almost couldn't speak. Eight years of nightmare over."
Ms Knox had also been convicted of slander for having falsely accused a Congolese man of the murder. That conviction was upheld by the high court tonight, but Ms Knox has already served the three-year sentence in prison.