Courtois, who finally returned to Stamford Bridge in the summer following three seasons on loan at Atletico Madrid, has played a key role in helping Chelsea remain unbeaten in the early stages of the season.
De Gea is one of the many people who have been impressed by the Belgian's form, and he claims that the 22-year-old should be considered one of the best goalkeepers in the world.
"I saw him at Atletico Madrid. He played very well. He's a great goalie," the Spaniard told reporters.
"He's young, he's big, he's a good shot stopper and he's good with crosses. He is one of the best."
Chelsea have conceded just eight goals in their eight Premier League fixtures this season.