AC Milan have signed Italy defender Leonardo Bonucci from Juventus for a reported 40m euros (£35.1m).
Bonucci has signed a five-year deal with the 18-time champions, who have spent about £160m this summer.
The Italy international, capped 70 times, joined the Milan club last week subject to a medical.
The 30-year-old spent seven years at Juventus, making 319 appearances and winning six consecutive Serie A titles.
Milan coach Vincenzo Montella said: “Technically, I think that he and Sergio Ramos are the strongest central defenders in the world.”
Bonucci becomes the fourth defender AC Milan have signed this summer following the arrivals of centre-back Mateo Musacchio from Villarreal for £16m, left-back Ricardo Rodriguez from Wolfsburg for £16mand right-back Andrea Conti for £21.4m.
AC Milan have also brought midfielders Franck Kessie, Hakan Calhanoglu and Lucas Biglia, along with forwards Andre Silvaand Fabio Borini, in what has been a very busy summer so far in the transfer market.
The Rossoneri are also in talks to sign Andrea Belotti from Torino after missing out on Alvaro Morata and Pierre- Emerick Aubameyangand have held discussions with Bayern Munich about signing Portuguese midfielder Renato Sanches.
Meanwhile, Juve completed the signing of full-back Mattia de Sciglio, 24, from Milan for £10.64m.
De Sciglio moves in the opposite direction as a replacement for Dani Alves at right back for Juventus.
Alves was released by Juventus in June and subsequently joined Paris Saint-Germain.
A statement on their website said: “Juventus are adding a player with versatility, skill and an international pedigree.”
Bonucci’s move means he becomes the world’s most expensive player aged 30 or over, surpassing the £22.5m Roma paid Fiorentina for striker Gabriel Batistuta in 2000.