Clement Lenglet has made 160 appearances for Barcelona since joining them from Sevilla in 2018
The deal is reported to have an option-to-buy clause included.
Lenglet, 27, struggled to cement his place in Barcelona's first XI last season, starting just seven La Liga matches.
The Catalan club signed Lenglet from Sevilla for 35.9m euros (£32m) in 2018 and added a 300 million euro (£265m) release clause to his contract.
He becomes Antonio Conte's fifth summer signing following the arrivals of Ivan Perisic, Fraser Forster, Yves Bissouma and Richarlison.
Lenglet has won 15 caps for France since making his debut in 2019 and has made a total of 160 appearances for Barcelona, helping them win the 2018-19 La Liga title and the Copa de Rey in 2021.
-- Courtesy of BBC Sport