The Old Lady have chosen ex- Italian national team head coach Spalletti to take the helm until the end of the season.
Spalletti replaces his predecessor, who was let go after the Serie A side's defeat by Lazio on Sunday.
Tudor had joined the club in March filling the shoes of Thiago Motta but left after seven months at the end of an eight-match winless run.
Spalletti led Napoli to the Serie A title in 2022-23 prior to assuming the Italy role, who had failed to qualify for the 2022 World Cup with Mancini at the helm.
Under his guidance, they made it to Euro 2024 but were eliminated in the round of 16 by Switzerland.
Nonetheless, Italy dismissed Spalletti in June after a World Cup qualifying defeat by Norway, with the Azzurri at risk of missing out on a third consecutive World Cup.
He has previously coached Inter Milan, Roma, and Udinese in Italy's top flight and won the Russian Premier League twice with Zenit St Petersburg.
Massimo Brambilla took interim charge of Juventus during the 3-1 victory over Udinese on Wednesday which left them seventh in Serie A - trailing leaders Napoli by six points after nine matches.
They are 25th in the league phase of the Champions League, having lost once and drawn twice in their opening three matches.
