The 23-year-old has agreed to terms on a five-year deal, becoming Eddie Howe’s first acquisition of the summer as his team prepares for Champions League play.
With a rumoured cost of £55 million, he would become the most expensive Italian player of all time.
Tonali helped Milan win Serie A in 2021-22 and was a member of the team that reached the Champions League semi-finals last season.
He also played for Italy at the Under-21 European Championships.
“I want to repay the trust on the pitch, giving it my all, as I always have,” Tonali said on the club’s website. I’m definitely looking forward to playing at St. James’ Park and feeling the affection of the supporters.”
Newcastle head coach Howe said of Tonali: “He is an exceptional talent and has the mentality, physicality and technical attributes to be a great fit for us.
“At 23, Sandro already has important experience as a key player in one of Europe’s top leagues and in the Champions League, as well as playing for his country.
“But he also has the opportunity and potential to grow and evolve with us, and I’m excited to add him to our squad as we approach the exciting season ahead.”
Tonali rose through the ranks at Brescia, making his professional debut in Serie B at the age of 17.
Tonali made his Italy debut as a substitute against Liechtenstein in October 2019 after Brescia was promoted to Serie A in 2018-19. Despite the club being demoted the following season, Tonali made his Italy debut as a replacement against Liechtenstein in October 2019.
In the summer of 2020, he joined AC Milan on loan and, after making the move permanent the following year, he scored five goals in 36 top-flight games as the team won the Italian title in 2022.
Tonali scored twice in 34 Serie A games as Milan finished fourth last season, and he made 12 Champions League appearances before losing to rivals Inter.
