The 35-year-old striker rejoins the Viola after five years away from the Artemio Franchi, as the club act quick to counter Dimitar Berbatov's rebuffal earlier in the week
The deal, believed to be worth around €500,000 to the striker, comes shortly after the Viola missed out on Dimitar Berbatov, who rejected their advances in favour of a move to Fulham.
The veteran enjoyed a hugely successful two-year stint in Florence before moving onto Bayern Munich in 2007, and five years later, the club have now confirmed the return of the 2006 World Cup winner.
"Fiorentina officially announce the outright purchase of Luca Toni," reads a statement on Fiorentina's official website.
"The striker, 35, returns after five years, having previously scored 49 goals in 71 appearances."
In an interview with Tuttomercatoweb, a delighted Toni remarked: "I'm going home, I'm happy. Tomorrow morning I will be in Florence to perform necessary the medical examinations."