Leonardo Bonucci has rejoined Juventus from AC Milan just a year after his dramatic exit from the Italian champions, with the striker Gonzalo Higuaín moving in the opposite direction.
AC Milan will pay 18m euros (£16m) for the loan of Higuain and have the option to make the deal permanent in a year by paying a fee of 36m euros (£32.04m).
Italy defender Mattia Caldara has left Juve to join AC Milan. Bonucci, 31, and Caldara, 24, is a swap deal with both transfers worth 35m euros (£31.2m).
Higuain, 30, scored 16 Serie A goals last season but became surplus to requirements after the sensational arrival of Cristiano Ronaldo from Real Madrid earlier in the summer.
A Juventus statement said: “After spending seven wonderful years in black and white, Leonardo Bonucci has returned to the club following a season at AC Milan.
“Both Juventus and Bonucci are ready to start winning things again together.”