Tielemans will leave relegated Leicester City at the end of this month when his contract expires.
The Belgium international had been linked with the likes of Arsenal and Liverpool but has chosen to link up with Unai Emery's side.
Tielemans initially joined Leicester on loan from AS Monaco in January 2019 before sealing a £40m move to the King Power Stadium that summer.
The 26-year-old made 195 appearances in total for Leicester, scoring 28 goals, including the winner in the 2021 FA Cup final against Chelsea.
Tielemans made 31 appearances and scored three goals this season but Leicester suffered relegation to the championship after a poor campaign.
A statement on the club’s official website said: “Aston Villa is delighted to announce that the club has reached an agreement to sign Youri Tielemans.
“The Belgian international will officially become a Villan on July 1 after his contract with Leicester City has expired.”
Aston Villa finished seventh in the Premier League this season and will play in the Europa Conference League next term.
Tielemans has played 58 times for the Belgium national team, scoring five goals.
