But De Ligt says leaving Ajax leaves him with mixed emotions.
“I played for 10 years in the youth sector and three in the first team, but unfortunately I have to take a step forward now," the 19-year-old told Ajax TV.
“I've always been fascinated by the Italian art of defending. Many of the players I look up to are Italian: Maldini, Baresi, Nesta, Cannavaro, Scirea... I could go on.
“I fell in love with how Italian clubs defend. For me, it's sad to leave Ajax. I experienced some wonderful and very ugly moments.
“It was like being on a rollercoaster, but there's always a time in our lives when we have to go our separate ways.
“I'll miss everyone, but no-one knows what the future holds."