Juventus have named former Azzurri head coach the veteran manager to lead the team for the rest of the term.
Spalletti replaces his predecessor, who was sacked after the Serie A side's defeat by Lazio last weekend.
Tudor had joined the club in March to replace Thiago Motta but departed after seven months after an eight-game winless streak.
Spalletti guided Napoli to the Serie A crown in 2022-23 then moving on to lead the Italian national team, which missed out on the 2022 World Cup with Mancini at the helm.
He helped them qualify for Euro 2024 but were eliminated in the round of 16 by Switzerland.
Nonetheless, Italy dismissed Spalletti in June post a qualifying defeat against Norway, putting Italy in danger of missing a third straight World Cup.
Spalletti has also managed Inter Milan, Roma and Udinese in Serie A and lifted the Russian league trophy twice while at Zenit St Petersburg.
Massimo Brambilla served as interim manager for Juventus during the 3-1 victory over Udinese on Wednesday moving them to seventh position in the league - six points behind leaders Napoli after nine games.
They are 25th in the league phase of the Champions League, after recording one defeat and two ties in the initial three fixtures.
