Norwegian midfielder Kristoffer Ajer has agreed to join Celtic in June on a four-year contract.
The 17-year-old is currently with Start in his homeland and had a trial with the reigning Scottish Premiership champions in January.
He returned to Glasgow for signing talks on Tuesday.
Ajer has made more than 40 senior appearances at club level, scoring 13 goals, and has played and scored for Norway Under-17s.
The teenager is the youngest player to captain a team in the Tippeligaen, which is presently in its close season.
He flew to Scotland from Alicante, where he had been at a pre-season training camp in La Manga.
And speaking after arriving at Glasgow Airport on Tuesday, Ajer said: "I'm really happy. I enjoyed it last time."
Celtic bolstered their first-team squad during the winter transfer window by signing Denmark defender Erik Sviatchenko and Turkey forward Colin Kazim-Richards and also brought in Manchester City's English winger Patrick Roberts.
Find all the latest football transfers on our dedicated page.