Juventus have appointed previous Italy head coach the veteran manager to take the helm for the rest of the term.
The experienced coach steps in for Igor Tudor, who was let go 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 before taking charge of Italy, which missed out on the 2022 World Cup with Mancini at the helm.
Under his guidance, they made it to Euro 2024 exiting in the last 16 stage against 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's managerial career includes Inter Milan, Roma, and Udinese in Serie A and won the Russian Premier League twice with Zenit St Petersburg.
Massimo Brambilla took interim charge of Juventus during the 3-1 victory over Udinese on Wednesday placing them seventh in the Serie A standings - 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.
