The Citroën driver needed to finish in the top three to secure his second world title and end the slim hopes of Marcus Gronholm and Petter Solberg.
He had been on course to do that all weekend but received an unexpected boost when Solberg crashed his Subaru out of the lead to promote Loeb to second place.
"It is fantastic," said Loeb, who finished over a minute behind winner Gronholm's Peugeot. "We have reached the first peak of what has practically been a perfect season by sewing up our second drivers' title with three rounds still to come.
"Each time out, Citroën has given us a competitive and reliable car. This triumph is also theirs and we now intend to do all we can to make sure the team keeps the manufacturers' title. They really deserve it."
Citroën lead Peugeot by 22 points in the manufacturers' standings and Loeb's boss Guy Frequelin wants to complete a dominant season by adding another championship.
"All season the team has succeeded in giving Seb and co-driver Daniel Elena a car that has allowed them to win the world championship again.
"Winning the drivers' title is only half the job. We must now finish it by making sure we keep the manufacturers' crown."
Subaru rookie Chris Atkinson showed his best form of the season to creep up to third place for his first world championship podium.
But Subaru were left cursing Solberg's late retirement, which came when he crashed less than 20 miles from the end after damaging his suspension.
"It's shocking, I almost can't believe it," Solberg said. "We could do nothing to avoid the rock, it was right in the line, it happened so fast and that was that. I'm absolutely gutted. There's nothing more to say."
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