Still waiting for his first appearance for the Blues, the Belgian goalkeeper will return to Spain for another year having impressed there last term as they won the Europa League
Courtois, who is yet to make a first-team appearance for the Blues since joining them from Racing Genk in 2011, is highly-rated by staff at Stamford Bridge, and is seen as a long-term successor to current first-choice goalkeeper Petr Cech.
"Thibaut Courtois will play next season at Atletico Madrid after an agreement was reached on Wednesday with Chelsea for a season-long loan," the Spanish club confirmed in a statement.
The Belgian goalkeeper's first season in Madrid saw him make 37 appearances in La Liga and another 15 in Europe as the side won the Europa League.
Courtois also made his debut for Belgium in a friendly against France in Paris last season, and wore the No. 13 shirt vacated by David de Gea after his move to Manchester United.