The ancient Greek statue is believed to have been made by Alexander the Great’s personal sculptor between 300 and 100 BC.
The statue was discovered by fishermen off Pesaro, on Italy’s Adriatic coast, in 1964.
It was sold several times, and eventually bought by the American museum over 40 years ago.
Italy has always claimed the statue was smuggled out of the country and bought illegally, making its first formal request for its return from the museum in 1989.
The ruling is the latest development in a decades-long clash between Italy and the American museum over the ownership of the statue, which is known as Victorious Youth, Athlete from Fano and the Getty Bronze.
“We now hope that the US authorities will act as soon as possible to favour the restitution of the statue to Italy,” Italy’s culture minister, Alberto Bonisoli, told ANSA.
“Let’s hope the statue can soon return to be admired in our museums.”
Pesaro prosecutor Silvia Cecchi told Italian media that the supreme court ruling was “the final word from the Italian justice [system]” and that the Lysippos masterpiece “must be returned”.
However, the legal battle looks far from over as the museum immediately vowed to defend its “legal right” to the statue.
“The court has not offered any written explanation of the grounds for its decision, which is inconsistent with its holding 50 years ago that there was no evidence of Italian ownership,” Lisa Lapin, Getty’s vice-president of communications, said in a statement.
“Moreover, the statue is not and has never been part of Italy’s cultural heritage. Accidental discovery by Italian citizens does not make the statue an Italian object. Found outside the territory of any modern state, and immersed in the sea for two millennia, the Bronze has only a fleeting and incidental connection with Italy.”
Experts refute this.
The fishermen who found the artefact sold it in Fano to Italian art dealer Giacomo Barbetti.
Barbetti kept the statue in his father’s home before it was transferred to the Umbrian town of Gubbio in 1965, where it was eventually sold to an unidentified buyer from Milan.
The statue then changed hands several times before being bought by the Getty from German art dealer Herman Heinz Herzer.
The sum paid was nearly 800 times the $7,700 that Italian art dealers gave to the fishermen who found it.