The Serie A powerhouse have named ex- Italian national team head coach Spalletti as their manager for the rest of the term.
The 66-year-old steps in for his predecessor, who was dismissed after the Serie A side's defeat by Lazio last weekend.
Tudor arrived at the club in March filling the shoes of Thiago Motta but left after seven months following a string of eight matches without a victory.
Under Spalletti, Napoli clinched the Serie A championship in 2022-23 before taking charge of Italy, after the team's failure to reach the 2022 World Cup with Mancini at the helm.
He helped them qualify for Euro 2024 exiting in the last 16 stage against Switzerland.
However, Spalletti was sacked by Italy in June after a World Cup qualifying defeat by Norway, with the Azzurri at risk of missing out on a third consecutive World Cup.
Spalletti has also managed Inter Milan, Roma and Udinese in Serie A and won the Russian Premier League twice with Zenit St Petersburg.
Massimo Brambilla served as interim manager for Juventus in the midweek 3-1 triumph over Udinese moving them to seventh position in the league - six points behind leaders Napoli after nine games.
In the Champions League, they sit 25th in the league phase, after recording one defeat and two ties in the initial three fixtures.
