The Serie A powerhouse have appointed former Azzurri manager Spalletti to take the helm until the end of the season.
The 66-year-old replaces his predecessor, who was let go post the Lazio setback last weekend.
Tudor had joined the club in March as Thiago Motta's replacement but left after seven months after an eight-game winless streak.
Under Spalletti, Napoli clinched the Serie A championship in 2022-23 prior to assuming the Italy role, who had failed to qualify for the 2022 World Cup under former boss Roberto Mancini.
He helped them qualify for Euro 2024 where they were knocked out in the last 16 by Switzerland.
Yet, the Italian FA let Spalletti go in June after a World Cup qualifying defeat by 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 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, with one loss and two draws in their first three games.
