Italy's top court has cleared Amanda Knox of the 2007 murder of British student Meredith Kercher.
Judges at the Court of Cassation also cleared Knox's Italian ex-boyfriend Raffaele Sollecito after ten hours of deliberations in Rome.
A Seattle-based representative for Ms Knox said he was "overjoyed" after her acquittal, adding that "the truth has won out."
"I personally feel overjoyed that the truth has won out, that she is innocent," said David Marriott, a spokesman for Ms Knox.
Mr Marriott referred additional questions to her US lawyer, calling the verdict "unexpected."
Ms Kercher, a 21-year-old from Coulsdon, Surrey, was sexually assaulted and stabbed to death in her bedroom in 2007 while studying in Perugia, Italy.
Her flatmate Ms Knox, a student from Seattle in the US, and Mr Sollecito spent four years in jail for the murder but were acquitted on appeal in 2011.
Ms Knox returned to the US before an appeal court threw out the acquittal and reinstated her and Mr Sollecito's guilty verdicts last year.
But Italy's highest court have overturned last year's convictions and declined to order another trial.
Ms Knox, who is now 27, awaited for the verdict in her hometown of Seattle. Her Italian former boyfriend Mr Sollecito, 30, had his travel documents seized while the court proceedings were ongoing.
The judges will release the reasons for their decision within 90 days after concluding that a conviction could not be supported by the evidence.
Prosecutors claimed that Ms Kercher, a Leeds University Student, was the victim of a drug-fuelled sex game gone wrong.
But Ms Knox and Mr Sollecito consistently protested their innocence and claimed they were not in the apartment the night she died.
Rudy Guede, a drug dealer, is serving a 16-year sentence over the death.
