Sebastien Loeb of France completed his 10th victory of the season in the Rally of Catalunya to seal the manufacturers' title for his Citroen team.
Loeb won nine stages of the Rally of Catalunya
Citroen claimed three of the first four places in the season's penultimate race, meaning they cannot be caught by second-placed Peugeot.
Belgian Francois Duval was second and Spain's Xavier Pons fourth, while Finn Mikko Hirvonen, in a Ford, was third.
The highest placed Peugeot driver was France's Nicolas Bernardi in sixth.
Loeb won just one stage on the final morning but with a comfortable advantage courtesy of two dominant days, he was never threatened.
Citroen only needed six points to be sure of the manufacturers' title while rivals Peugeot needed a one-two to keep the fight alive going into the final round in Australia.
But Marcus Gronholm's retirement overnight ended any slim hopes Peugeot had.
The Finn was running third but a leaking radiator caused a blown engine after Saturday's last stage and he was unable to start Sunday's action.
That lifted ex-works Subaru driver Hirvonen, now driving a private Ford, into a superb third place.
A high attrition rate among the top drivers helped some lesser lights break into the upper echelon of the leaderboard, with independent Citroen driver Pons earning a stunning fourth.
Catalunya Rally result:
1. Sebastien Loeb (France) Citroen 3:31:07.000
2. Francois Duval (Belgium) Citroen +01:21.900
3. Mikko Hirvonen (Finland) Ford 02:46.700
4. Xavier Pons (Spain) Citroen 02:47.900
5. Roman Kresta (Czech Republic) Ford 03:24.600
6. Nicolas Bernardi (France) Peugeot 04:09.400
7. Antony Warmbold (Germany) Ford 05:00.300
8. Jan Kopecky (Czech Republic) Skoda 05:22.300
9. Chris Atkinson (Australia) Subaru 05:40.200
10. Harri Rovanpera (Finland) Mitsubishi 07:39.300