The Serie A powerhouse have appointed former Italian national team head coach Spalletti to take the helm for the rest of the term.
The 66-year-old takes over from his predecessor, who was sacked after the Serie A side's defeat by Lazio last weekend.
Tudor had joined the club in March filling the shoes of Thiago Motta but departed after seven months at the end of an eight-match winless run.
Spalletti led Napoli to the Serie A title in 2022-23 then moving on to lead the Italian national team, who had failed to qualify for the 2022 World Cup during Roberto Mancini's tenure.
Under his guidance, they made it to Euro 2024 exiting in the last 16 stage against Switzerland.
Nonetheless, Italy dismissed Spalletti in June after a World Cup qualifying defeat by 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 secured two Russian Premier League titles with Zenit St Petersburg.
Massimo Brambilla took interim charge of Juventus for their 3-1 win against Udinese on Wednesday which left them seventh in Serie A - 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.
