The 22-year-old midfielder, who joined Chelsea from Genk in January 2012, has signed a contract until 2019 with the Bundesliga club
The 22-year-old, who moved to Stamford Bridge from Genk in January 2012, has signed a contract with the Bundesliga club which expires in 2019.
De Bruyne had made just nine appearances under Jose Mourinho this season and was criticised for his display during Chelsea's win over Swindon Town in the Capital One Cup in September.
The midfielder, who scored 10 goals during his season-long loan spell at Werder Bremen last term, had struggled to compete for a regular place at Stamford Bridge alongside Oscar, Eden Hazard, Juan Mata, Andre Schurrle and Willian.
De Bruyne has been capped 18 times by Belgium and is vying for a place in Marc Wilmots' squad for this summer's World Cup.