Chelsea midfielder Thorgan Hazard has agreed to join Borussia Monchengladbach on a permanent basis in the summer.
The 21-year-old Belgium international, whose older brother Eden plays for Chelsea, has spent this season on loan at the German Bundesliga side.
He has signed a contract until 2020, with the Premier League leaders retaining a buy-back option on him.
"In recent months Thorgan has shown how big a talent he is," said Gladbach sporting director Max Eberl.
"We're delighted to have signed him and that he has chosen to spend the coming years playing for us."
Hazard has made 29 appearances for Gladbach, scoring four goals and providing six assists.
He joined Chelsea from French side Lens in 2012, but has never played for the Blues' first team.
Hazard made 48 appearances for Belgian top-flight club Zulte last season, scoring 16 goals, having been named as the league's best player during a previous loan spell.