De Ligt agreed personal terms with Juventus last week that will see the defender earn €12m (£11m/$13m) per season – €8m in basic salary with €4m in bonuses.
And the 19-year-old has now finalised his move to Juve, who have seen off competition from a host of Europe’s top clubs, including Barcelona, Manchester United and Paris Saint-Germain.
He arrived in Turin on Tuesday and underwent a medical on Wednesday ahead of the completion of his move.
For Juventus, De Ligt is the club’s seventh signing of the transfer window as they look to win their first Champions League title since the 1995-96 season.
Adrien Rabiot, Aaron Ramsey and Gianluigi Buffon have been brought in on free transfers, while Luca Pellegrini was purchased from Roma, Merih Demiral arrived from Sassuolo, and Cristian Romero was signed from Genoa.