Courtois spent three seasons on loan with Atletico Madrid between 2011 and 2014, before returning to parent club Chelsea to replace Petr Cech as their number one goalkeeper.
The 26-year-old has been linked with a move to Real Madrid over the last 12 months or so amid suggestions that he does not want to sign a new contract at Stamford Bridge.
Courtois's current deal with Chelsea actually expires next summer, and the Belgian recently hinted that he wants to secure a return to Spain ahead of the 2018-19 campaign in order to be closer to his children.
The Blues stopper, however, has insisted that no firm decision will be made until after this summer's World Cup.
"My future? I'm not thinking about anything right now that isn't the World Cup," Courtois told Onda Cero.
Courtois's Belgium team will take on France in the semi-finals on Tuesday night.