De Ligt had also been linked with Manchester United, Barcelona and Paris Saint-Germain after his impressive performances for a young Ajax side that reached the Champions League semi-finals last season.
At the weekend Leiderdorp-born De Ligt was left out of Ajax's squad for their summer tour to Austria pending a transfer and he arrived in Turin on Wednesday to undergo a medical at Juve's headquarters.
Barcelona and PSG were also interested in the Dutch football player.
Ajax knew they faced a battle to keep hold of him this summer and following his departure, they've released a video celebrating De Ligt's journey at the club.
Ronaldo had just led Portugal to only their second global trophy in history when he seemingly turned into "Agent Ronaldo" and was seen chatting to De Ligt after the final whistle.
Juve have already signed another young centre-back this summer in 21-year-old Turkey global Merih Demiral, brought in from Sassuolo, as Andrea Barzagli departed the club after eight seasons. The deal is reportedly worth up to 75 million euro. For a defender it is important to come to Italy.
He had seven goals for Ajax this past season including one to knock Juve out of the Champions League quarterfinals.
De Ligt in March 2018 became Ajax's youngest ever captain.
"That could be true, yes", he answered at the time, as quoted by AS, when asked if Ronaldo had told him to join him at Juventus.
The transfer fee is around EUR13 million ($14.6 million) plus two additional payments, according to media reports.