Calvin Ramsay, an 18-year-old right-back from Aberdeen, has signed a five-year contract with the Reds.
Potential add-ons and a 17.5% sell-on clause are included in the deal for the Scotland under-21 player.
Ramsay will join the first team for pre-season and there are no plans for him to go on a loan.
He scored one goal and had nine assists for Aberdeen.
After rising through the youth ranks, he has made 39 appearances for the club.
He was named young player of the year by the Scottish Football Writers' Association in April after an impressive breakthrough campaign that saw him linked with a host of European clubs.
He is the third player to join the club this summer, following the arrivals of Darwin Nunez and Fabio Carvalho.
The Carabao Cup and FA Cup were won by the Reds, but they were runners-up in the league and lost in the final of the European competition.
There's more to come.