The versatile defender has featured high on Juventus boss Max Allegri's summer shopping list ever since the departure of right-back Dani Alves.
With rumours continuing to circle over the future of left-back Alex Sandro, Allegri was keen to bolster his back-line and with reports in the Italian media placing De Sciglio's fee in the region of £10.6m, he comes considerably cheaper than some of Juve's back-up options, such as Manchester United's Matteo Darmian.
24-year-old De Sciglio has been a one-club man so far in his career, making 133 appearances for the 'Rossoneri' since making his debut in 2011.
Juventus announced De Sciglio's arrival ahead of his medical on the club website, with a statement reading: "Mattia De Sciglio arrived at J|Medical on Wednesday morning at approximately 9.00 CEST to undergo medical tests ahead of his proposed move to Juventus.
The 31-time Italy international made 27 appearances in all competitions for AC Milan last season.
Welcome to J|Medical @mattia_desci! pic.twitter.com/teVRHE65IM
— JuventusFC (@juventusfcen) 19 de julho de 2017