Juventus have chosen former Italian national team head coach Spalletti to take the helm for the remainder of the campaign.
The 66-year-old takes over from Igor Tudor, who was sacked post the Lazio setback last weekend.
The former boss came on board in March as Thiago Motta's replacement but departed after seven months 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, which missed out on the 2022 World Cup during Roberto Mancini's tenure.
He helped them qualify for Euro 2024 exiting in the last 16 stage against Switzerland.
Nonetheless, Italy dismissed Spalletti 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 has also managed Inter Milan, Roma and Udinese in Serie A and secured two Russian Premier League titles with Zenit St Petersburg.
Juventus were temporarily led by Massimo Brambilla during the 3-1 victory over Udinese on Wednesday moving them to seventh position in the league - six points adrift of Napoli at the top after nine rounds.
Their Champions League campaign sees them in 25th place in the group stage, after recording one defeat and two ties in the initial three fixtures.
