The 22-year-old, who joined the west Londoners from Belgian side KRC Genk in 2011, has replaced Petr Cech as Chelsea's first-choice goalkeeper this season after spending the previous three years on loan at Spanish champions Atletico Madrid.
"I'm very happy with this new deal. It's really nice to have signed this new contract for five years," Courtois told the club's website.
"My future was already sorted but it's nice to know I'm going to be here for another five years and now I can just concentrate on playing games," he said.
Courtois, who was part of the Belgian side that reached the World Cup quarter-finals in Brazil, is expected to start in goal for Chelsea's clash against Swansea City at Stamford Bridge on Saturday.

Latest News from Sports News Desk