Juventus have chosen previous Azzurri head coach the veteran manager to lead the team until the end of the season.
The 66-year-old takes over from his predecessor, who was let go post the Lazio setback recently.
Tudor arrived at the club in March to replace 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, which missed out on the 2022 World Cup under former boss Roberto Mancini.
He secured their spot in Euro 2024 where they were knocked out in the last 16 by Switzerland.
Nonetheless, Italy dismissed Spalletti in June post a qualifying defeat against 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 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 behind leaders Napoli after nine games.
They are 25th in the league phase of the Champions League, with one loss and two draws in their first three games.
