The Argentina U20 international is thought to be one of the best defensive prospects in world football and has signed a five-year deal with the Londoners.
The 19-year-old who can player either in the centre of defence or in a holding midfield role has made 12 appearances for the Argentina U20 side and made 6 appearances for club side Estudiantes La Plata last season.
Spurs are thought to have parted with £8m to sign Foyth, who becomes Mauricio Pochettino's third signing of the summer following Paulo Gazzaniga and Davinson Sanchez.
Foyth is likely to go staight into Spurs' development side.
We are delighted to announce the signing of Juan Foyth from Estudiantes. #WelcomeFoyth pic.twitter.com/PAc2VuBkpn
— Tottenham Hotspur (@SpursOfficial) August 30, 2017