Juventus have named former Azzurri manager Spalletti to lead the team until the end of the season.
The 66-year-old steps in for Igor Tudor, who was sacked 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.
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 under former boss Roberto Mancini.
Under his guidance, they made it to Euro 2024 where they were knocked out in the last 16 by Switzerland.
However, Spalletti was sacked by Italy in June following a loss to Norway in World Cup qualifying, as Italy faced the possibility of not making a third World Cup in a row.
Spalletti has also managed Inter Milan, Roma and Udinese in Serie A and won the Russian Premier League twice with Zenit St Petersburg.
Juventus were temporarily led by Massimo Brambilla in the midweek 3-1 triumph over Udinese which left them seventh in Serie A - six points behind leaders Napoli after nine games.
In the Champions League, they sit 25th in the league phase, with one loss and two draws in their first three games.
