The 22-year-old winger moves to Florence on a loan worth around 1million euros, with Fiorentina holding the option to make the deal permanent for a further 15million euros at the end of the season.
Sporting director Fabio Paratici pushed the deal through late in the window to give head coach Fabio Grosso another attacking option on the flanks, having already brought in Beto from Everton and winger Njie earlier in the summer.
Born in Verbania on 5 November 2003, Gnonto came through Inter Milan's youth ranks before beginning his senior career at Zurich and then moving to Leeds United, where he made 65 appearances across the Premier League, FA Cup and EFL Cup, scoring six goals and providing eight assists. He returns to Italian football having spent his career to date entirely abroad since leaving the Inter academy.
Gnonto has also made 13 appearances for the senior Italy national team, scoring once, a goal that made him the youngest scorer in the Azzurri's history. His versatility across the front line and pace in behind defences were key factors in Fiorentina's decision to move for him late in the window, with Leeds only granting their approval for the move once satisfied over squad cover for the position he vacates.
The move gives Fiorentina considerable strength in depth across the attacking positions heading into the new season, adding a proven Serie A-calibre wide player to a forward line already reshaped significantly over the summer.
Gnonto's return to Italy comes after four years away from the domestic game, having left the Inter academy to build his career first in Switzerland and then in England.
He joined Leeds on a five-year deal in 2022 and became a regular contributor for the Yorkshire club across four seasons, establishing himself as a full Italy international along the way despite his relatively modest height for a wide attacker. Fiorentina's technical staff view him as a player who can operate on either flank, offering Grosso genuine tactical flexibility as the club look to build on last season's form.