The Serie A powerhouse have named ex- Azzurri head coach Spalletti to take the helm for the rest of the term.
The 66-year-old takes over from his predecessor, who was dismissed post the Lazio setback recently.
Tudor arrived at the club in March as Thiago Motta's replacement but departed after seven months at the end of an eight-match winless run.
Under Spalletti, Napoli clinched the Serie A championship in 2022-23 then moving on to lead the Italian national team, after the team's failure to reach the 2022 World Cup under former boss Roberto Mancini.
Under his guidance, they made it to Euro 2024 but were eliminated in the round of 16 by Switzerland.
Yet, the Italian FA let Spalletti go in June after a World Cup qualifying defeat by Norway, putting Italy in danger of missing a third straight World Cup.
Spalletti's managerial career includes Inter Milan, Roma, and Udinese in Serie A and lifted the Russian league trophy twice while at Zenit St Petersburg.
Juventus were temporarily led by Massimo Brambilla for their 3-1 win against Udinese on Wednesday which left them seventh in Serie A - six points adrift of Napoli at the top after nine rounds.
Their Champions League campaign sees them in 25th place in the group stage, having lost once and drawn twice in their opening three matches.
