The 18-year-old exchange student told a court hearing in Naples was raped twice in a night.
The teen said she was first attacked by two men after leaving a bar in Naples.
She said she was raped by the two men, who left her alone at the side of the road. Following the attack when another man came by and tried to offer her help, but then proceeded to rape her as well, the court heard.
The second attacker abandoned her close to a police station, where she filed a report.
Prosecutors say they discovered a series of messages from the men, who allegedly boasted about the attack.
A spokesman for the prosecution team said: “They claim the sex was consensual.”
The hearing was adjourned as police carry out more investigations into the attack.
Every year, thousands of British tourists flock to Naples – located in Italy’s southern region, known as the Mezzogironia – the largest city in Italy after Rome and Milan.