Real Madrid land Varane from Lens
The 18-year-old youth international made his debut in Ligue 1 with Lens last November and went on to make 23 league appearances.
Local media reported Jose Mourinho's side would pay around 10 million euros.
The towering centre-back, who can also operate in a midfield holding role, will be competing with players such as Pepe, Ricardo Carvalho, Raul Albiol and Ezequiel Garay for a place in the centre of defence next season.
Varane is Real's fourth signing of the close-season after Turkish midfielders Nuri Sahin and Hamit Altintop, and Spanish striker Jose Callejon.