The Serie A powerhouse have appointed ex- Italian national team manager Spalletti as their manager until the end of the season.
The 66-year-old steps in for his predecessor, who was let go post the Lazio setback on Sunday.
Tudor arrived at the club in March as Thiago Motta's replacement but exited following a seven-month stint following a string of eight matches without a victory.
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 during Roberto Mancini's tenure.
He secured their spot in Euro 2024 exiting in the last 16 stage against Switzerland.
Yet, the Italian FA let Spalletti go in June after a World Cup qualifying defeat by Norway, as Italy faced the possibility of not making a third World Cup in a row.
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.
Juventus were temporarily led by Massimo Brambilla for their 3-1 win against Udinese on Wednesday which left them seventh in Serie A - trailing leaders Napoli by six points after nine matches.
Their Champions League campaign sees them in 25th place in the group stage, having lost once and drawn twice in their opening three matches.
