Amanda Knox will fly home to the US after she and ex boyfriend Raffaele Sollecito were cleared of Meredith Kercher’s murder.
After 11 hours of jury deliberations both were acquitted "for not committing the act", the judge said.
The decision followed an independent review of the forensic evidence.
Knox, who has spent four years of a 26 year sentence in prison, broke down in tears when the verdict was read out last night.
Knox’s parents who travelled from Seattle for the verdict, hugged their lawyers and wept with joy at when the verdict was handed down, effectively overturning Knox and Sollecito’s convictions.
In a statement Knox's sister Deanna said: "(Amanda) has suffered for four years for a crime that she did not commit."
But others were not so jubilant. Some rubberneckers outside the court shouted "Shame, shame!" while another observer shouted: "Run off back to America on your private jet," when the verdict arrived.
The Kercher family meanwhile did not betray any emotion when the verdict was read out.
British student Meredith Kercher was found dead with her throat cut in the Perugia house she shared with Knox in 2007.
Knox and Sollecito were subsequently found guilty of the murder despite protesting their innocence.
Rudy Guede was convicted of the murder in a separate trial.
Although cleared of murder the court upheld Knox's previous conviction for slander, for falsely accusing bar owner Diya "Patrick" Lumumba of commiting the crime.