AC Milan have announced that the Italian defender has signed a one-year contract with the club.
The deal is reportedly worth around €6m, with the first year free.
“I am really happy to sign for AC Milan,” Florenzia told the club’s official website.
“I am very grateful to the management and I am really looking forward to the new challenge in the new season.”
The former Inter player, 27, will have the option of leaving the club after one year and can still be offered a new contract if he is not happy with the deal.