The Portuguese superstar, who arrived at the Bernabéu for a world record fee in 2009, moved to the Italian champions for a reported fee of 105 million euros after breaking Real Madrid's scoring record and landing four Ballons d'Or and four Champions League titles during his Bernabéu career.
The signing also strikes a blow for the profile of Serie A against La Liga, which has now lost two of its three most famous players in the past year after Paris Saint-Germain signed Neymar from Barcelona last August.
Ronaldo, however, soured the celebrations immediately after the 3-1 win over Liverpool in the final in Kiev by indicating he had made a decision to leave, saying in a post-match interview "It was attractive to play for Real Madrid".
He is also a five-time world player of the year, a record he shares with his eternal rival, Argentine talisman Lionel Messi.
In a letter posted on Real's website, the multiple Ballon d'Or victor said his time in Madrid had been one of the happiest in his life.
In Real Madrid'sstatement on the website, they said: "Cristiano Ronaldo will always be one of the greatest symbols of the club and a unique reference for the next generation".
"In addition to the titles he won, Cristiano Ronaldo has been an example of dedication, work, responsibility, talent and determination", Madrid added. "I came here to win titles", the 24-year-old told reporters.
Real Madrid has won my heart and that of my family and it is because of that, now more than ever, I would like to say thank you.
He scored 451 goals for the side in 438 games, and won 17 major trophies in total.
Jeremy Hunt named UK's new foreign minister to replace Johnson
In her statement Prime Minister vowed to deliver "a Brexit that is in our national interest, the right Brexit deal for Britain". Under Conservative Party rules, a leadership race could be triggered if at least 48 of her MPs declared their support for one.
DAMN YANKEES Star Tab Hunter Dies at 86
Just a couple of years later, he shot to fame after making an impression with his muscle-bound appearance in Island of Desire . And this guy said, 'Turn around Tab , this is for the next issue of Confidential magazine.' I went, 'Oh God!' and turned away.