The 33-year-old joined the Serie A side in a move worth €100m (£88m/$117m) plus €12m (£10.5/$14m) in additional charges, while he committed to a four-year contract that will see him net €30 million (£26.5m/$35m) each season.
Juve tried to sign Ronaldo when he was just 18, only to see the move fall through and the attacker to become a star at Manchester United and then Madrid.
This time, however, it was the Portuguese icon who got in touch with the Bianconeri, as he sought a way out of the Spanish capital following their Champions League win.
While his agent, Jorge Mendes, was in talks with the Bianconeri over Joao Cancelo's move to Turin, the forward made first contact with the Italian champions, leaving them with an easy decision to make.
"I'm happy, very happy," Marotta told Corriere della Serra after landing the five-time Ballon d'Or winner. "The real protagonists of this team are the player himself and the Juventus shareholders.
"It was Cristiano Ronaldo who was the first to believe in this, the first to launch it. He chose Juve, and when we understood that we could seize this opportunity, the shareholders of the club agreed to support the move. I insist, it was a great team game.
"It all began when we started dealing with Joao Cancelo, who has the same agent of Ronaldo."
The signing has proved an exciting one for Juve fans and figures across the football world. Former Bianconeri and Italy star Alessandro Del Piero hopes Ronaldo can lead his new side to Champions League glory, just as he did United and Madrid. Meanwhile, Brazil icon Pele said he made the "right move" in seeking a "new challenge".