Bournemouth have signed Lewis Cook from Leeds United on a four-year deal for a fee of £7m rising to £10m with add-ons.
Cook, 19, is one of the Championship's hottest prospects.
Bournemouth boss Eddie Howe tried to sign the 19-year-old in the January transfer window, but then-United boss Steve Evans kept hold of him.
A product of the Leeds academy, the central midfielder was named Football League Young Player of the Year last season.
Previous winners of that award include Gareth Bale and Dele Alli.
AFC Bournemouth chief executive Neill Blake said, "We're pleased to be bringing one of the country's brightest prospects to the club.
"Lewis has impressed since earning his spot in the Leeds United first-team and we feel that he can continue his rapid progress under the tutelage of Eddie and Jason.
"He's represented England at youth level and won plenty of individual awards last season, we're excited to see him flourish further at Vitality Stadium over the next four years."
Leeds have been busy in the market already this summer, adding six new signings, the latest being Swansea midfielder Matt Grimes - who arrives on loan - and Oxford United striker Kemar Roofe.