The Serie A powerhouse have named previous Italian national team manager Spalletti to lead the team for the rest of the term.
Spalletti replaces his predecessor, who was sacked post the Lazio setback last weekend.
The former boss came on board in March filling the shoes of Thiago Motta but exited following a seven-month stint at the end of an eight-match winless run.
Spalletti led Napoli to the Serie A title in 2022-23 then moving on to lead the Italian national team, which missed out on the 2022 World Cup with Mancini at the helm.
He secured their spot in Euro 2024 exiting in the last 16 stage against 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 took interim charge of Juventus for their 3-1 win against 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, having lost once and drawn twice in their opening three matches.
