The 19-year-old former Anderlecht and Club Brugge academy player joined the Potters’ youth structures in 2013 and has played six times for the first team.
His ability and attitude has seen him handed a five-year contract after being linked with the likes of Monaco in the off-season.
Stoke chief executive Tony Scholes revealed his delight at having tied down the Belgium U21 international.
He told the club’s official website: “Julien is an exciting young talent who has made excellent progress in the last couple of years and he’s fully deserving of a new long-term deal.
“It’s pleasing that another of our up-and-coming players has decided to pledge his future to the club.”