In signing the 22-year-old, Spurs have eclipsed the £42m spent on defender Davinson Sanchez in 2017.
“We are delighted to announce the signing of Tanguy Ndombele from Olympique Lyonnais”, the club said in a statement. “The France international central midfielder has signed a contract with the Club until 2025.”
Ndombele was a crucial player in the base of midfield for Lyon last season, making 34 appearances in Ligue 1 and helping the club qualify for the Champions League with a third-placed finish.
Earlier on Tuesday, Tottenham have signed 18-year-old winger Jack Clarke fromLeeds United– their first signing since January 2018.
Clarke, who has penned a five-year deal, will return to the Championship side on loan for the 2019-20 season.
“I’m delighted to join Tottenham and in the short term I’ll be giving my all to hopefully help Leeds win promotion,” he told the club’s official website.
Clarke played 25 times for Leeds in all competitions last season, grabbing two goals and two assists underMarcelo Bielsa.
Spurs had gone two transfer windows without signing a player, with Lucas Moura the last arrival fromParis Saint-Germain18 months ago.
Additional reporting from Reuters