Riccardo Calafiori has signed a five-year contract with Arsenal and joined the squad in Philadelphia today.
The deal for the 22-year-old Bologna defender, who can play at centre back or left back, is worth around £42million.
It ends weeks of speculation linking the Italian to the Gunners, and is the first addition to Mikel Arteta's squad this summer.
Calafiori was a key player last season for Bologna, the Serie A team securing Champions League qualification for the first time in six decades.
He then shone in Italy's Euro 2024 campaign, starting all three of their group stage matches.
Arsenal have officially unveiled Riccardo Calafiori after sealing a £42m deal for the defender
Calafiori has joined from Bologna and already linked up with his team-mates in Philadelphia
Calafiori's arrival was officially announced to his new team-mates during a squad meeting at Arsenal's team hotel and he delivered a brief message after standing up.
'Of course, I'm really happy to be here,' he said. 'I waited a lot.
'I hope we are going to do something great this year. Just this. Thank you.'
The versatile addition then shared a warm embrace with Arteta shortly after the briefing and was caught on camera asking, 'Is this real?'
A beaming Arteta responded, saying: 'It's real. It's real. Finally, it's real.'
Calafiori played 30 times for Bologna in the Italian top-flight last season, scoring two goals and recording five assists, and has been lauded by Arteta as a 'great signing'.
The 22-year-old delivered his first message to the squad during a team meeting at the hotel
He was later caught on camera asking whether his belated switch to the club was 'real'
Calafiori impressed last season at club level and was ever present for Italy at Euro 2024
'Riccardo is a big personality and character, with specific skills which will make us stronger as we push to win major trophies,' Arteta added.
'He has already shown great development with his performances for both Bologna and Italy, with his progression and development in the past year really impressive.
'We're looking forward to working with Riccardo, integrating him into the squad, and supporting him in the years to come.'
Further transfers are expected before the window closes on August 30 as Arteta looks to bolster his squad for another tilt at the Premier League title.
The deal follows the activation of goalkeeper David Raya's option-to-buy clause in his loan contract earlier this month.