The 18-year-old, who played eight times for Rovers in the Championship last season, has signed a five-year deal.
Tottenham sign England Under-19 defender from Blackburn Rovers.
He joined Blackburn Rovers as a 12-year-old in 2017 and worked his way through the academy before making his first-team debut in 2022.
Tottenham activated his £2 million release clause, making him the club’s sixth summer acquisition under new manager Ange Postecoglou.
They also signed England midfielder James Maddison from Leicester City for £40 million, Italian goalie Guglielmo Vicario from Serie A club Empoli, and Israel winger Manor Solomon on a free transfer after leaving Shakhtar Donetsk.
Juventus loanee Dejan Kulusevski of Sweden and Sporting Lisbon loanee Pedro Porro of Spain have both been made permanent.
“I’ve matured so much at such a young age, and it really means a lot,” Phillips added, thanking Blackburn for helping him develop his talent.
“Blackburn Rovers will always have a place in my heart and I wish the club all the best going forward.”
Phillips has been a regular in England’s youth set-up since he switched his allegiance from Wales in 2021 and he captained England Under-18s against Norway in June.
Tottenham’s 2023-24 Premier League campaign begins away at Brentford on Saturday, 13 August.
