"I believe that the time has come to begin a new stage in my life and that is why I have asked the club to accept my transfer request".
In a letter posted on the Real website, the five-time Ballon d'Or victor said his time in the Spanish capital, during which he became their record goalscorer, had been one of the happiest in his life.
Real's all-time top scorer, Ronaldo is reported to have signed a four-year contract that will see him pocket €30 million (£26.5m/$35m) per season.
What many people thought was the rumour of the summer has turned into the transfer of the summer after the Italian champions confirmed that a deal for the 33-year-old had been completed.
"They have been nine unique years", added Ronaldo.
He also scored a hat-trick for Portugal in the World Cup and netted a spectacular bicycle kick against Juventus in the Champions League in the spring.
Journalist Guillem Balague tells Sky Sports that the four-year deal could end up costing Juventus €400m (£354m) but notes that in the two days leading up to the deal the club's stock market value rise by 20%.
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 St Germain signed Neymar from Barcelona last August.
And it is that kind of ambition that will keep the Belgian in London, who wants to win the Champions League.
But they are not the only ones with faith in one of the best players of all time, with Juventus' shares on the stock exchange spiking by nearly 40 per cent since rumours of Ronaldo's arrival first surfaced on June 28, and by 5.7 per cent yesterday alone. Both players pushing each other to become better than they otherwise could have been.