The 19-year-old, whose parents moved from Barrhead to start a new life in Spain, joined the Spanish giants as a 13-year-old and still had two years left on his contract.
Harper had established himself in the world famous club's youth ranks, but it seems a decision to disband the Real C team had put his future under threat, leading to his move to England.
Harper hit the headlines earlier this year when he was dropped from the Scotland under-19 squad by boss Ricky Sbragia. However, he still holds aspirations of playing for the country despite being born on the Costa del Sol.
The English Championship side unveiled their new signing this morning, with Harper ditching Madrid to join Chris Hughton's side ahead of the new season.
Brighton boss Hughton said: "Even at the age of 19, Jack is a well-known name and having spent the past six years at Real Madrid, there is no doubting his pedigree."
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