The Portugal star, 33, is to join reigning Serie A champion Juventus from the Champions League holder for a reported $117 million transfer fee.
"He's called Cristiano Ronaldo and he's now officially a Bianconero," read an announcement on the Juventus website Tuesday.
The club also confirmed that Ronaldo would sign a four year contract, tying him to Juve until 2022.
Real Madrid had earlier released a statement "expressing its gratitude to a player who has proved to be the best in the world and who has marked one of the brightest times in the history of our club and world football."
In an open letter to Real's fans, Ronaldo said that he had "reflected a lot" and knew that "the time has come for a new cycle."
Last season, the Portuguese star scored a stunning bicycle kick against Juventus in Turin, which was widely viewed as one of world's greatest ever Champions League goals.
Ronaldo had a barnstorming start to the World Cup scoring a hat-trick against Spain in a 3-3 draw, before Portugal was knocked out by Uruguay in the last 16 stage.