Juventus have activated the 40m euro purchase clause to sign winger Douglas Costa on a permanent deal from Bayern Munich.
The 27-year-old initially moved to Turin on loan for 6m euros last summer with a 40m euro option to buy.
And the Brazilian was one of the key players for Massimiliano Allegri as the club wrapped up a seventh straight Serie A title and fourth Italian Cup in a row.
"Juventus have exercised the option for the definitive acquisition of the registration rights of Douglas Costa from Bayern Munich for EUR40 million to be paid in two financial years," Juve said in a statement.
"Juventus and the player signed a contract of employment until 30 June 2022."
Juventus added that the German champions could be paid a further fee of 1m euros depending on Costa's future performances.
Costa scored six goals and contributed 14 assists in 47 competitive games during his first season in Italy.
He completed the highest number of dribbles in Serie A, with 106.
Costa joined Bayern from Shakhtar Donetsk for 30m euros in 2015, but struggled to follow up on his strong debut season in the 2016/17 campaign before moving to Italy.