Juventus have chosen previous Italy manager the veteran manager to lead the team until the end of the season.
Spalletti replaces his predecessor, who was dismissed following the loss to Lazio recently.
Tudor had joined the club in March as Thiago Motta's replacement but left 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, which missed out on the 2022 World Cup during Roberto Mancini's tenure.
He secured their spot in Euro 2024 where they were knocked out in the last 16 by Switzerland.
Yet, the Italian FA let Spalletti go in June following a loss to Norway in World Cup qualifying, with the Azzurri at risk of missing out on a third consecutive World Cup.
Spalletti's managerial career includes Inter Milan, Roma, and Udinese in Serie A and secured two Russian Premier League titles with Zenit St Petersburg.
Massimo Brambilla served as interim manager for 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.
In the Champions League, they sit 25th in the league phase, with one loss and two draws in their first three games.
