Ogier, in a Volkswagen, wrapped up the crown in the Power Stage on the Rally of France's first day.
He was assured of the title when Belgium's Thierry Neuville, the only man who could delay the celebrations, managed just second place on the stage which was won by Spain's Dani Sordo in a Citroen.
Ogier was third while Loeb, who has only raced in four rallies in his retirement season, was down in seventh spot.
"The way we have won this title is amazing," Ogier told www.wrc.com.
"In a year we have gone from zero to world champions and it's such a great story. It's been a hard year with a lot of work, development, and effort from everyone. It's Volkswagen's first year in WRC and we have not finished the season yet, but already we are champions."
Neuville, in a Ford, needed to take the three points on offer to the winner of the Power Stage to keep his slim hopes of snatching the title alive.
But he now stands 82 points behind Ogier with just 81 left to fight for in the last three races -- in France, Spain and Great Britain.
Ogier, 29, and co-driver Julien Ingrassia, capped a fine first full season in the world rally championship for German manufacturer Volkswagen.
Loeb, 39, had pledged to push Ogier all the way in France, but his challenge fizzled out on Thursday.
"It was a strange feeling to realise I was champion, but I still had to drive the stage. I was shaking a lot inside the car and I didn't expect that," added Ogier after seeing Neuville finish the stage just 0.7sec behind Sordo.
"But I was happy because it meant that I had a lot of emotion, and sometimes I'm not emotional enough."
Neuville, who had needed to win the last three rallies while also hoping that Ogier would finish without another point, remained upbeat.
"We knew already that we couldn't really win, so it doesn't change anything," said the Belgian.
"What's important is that we were quicker here than Jari-Matti Latvala and I hope to get one or two more points this weekend. Can I win? I don't know, we will try, but we want second in the championship more, so points are the priority."
Mikko Hirvonen is fourth overnight, with Andreas Mikkelsen fifth and Latvala sixth. Loeb is seventh, 2.9sec off the lead.
Standings after the opening Power Stage of the Rally of France, the 11th event of the 13-leg world rally championship, in Strasbourg on Thursday:
1. Dani Sordo (ESP/Citroen DS3 3min 20.8sec, 2. Thierry Neuville (BEL/Ford Fiesta) at 0.7s, 3. Sebastien Ogier (FRA/VW Polo) 0.8, 4. Mikko Hirvonen (FIN/Citroen DS3) 1.4s, 5. Andreas Mikkelsen (NOR/VW Polo) 1.5s, 6. Jari-Matti Latvala (FIN/VW Polo) 2.6, 7. Sebastien Loeb (FRA/Citroen DS3) 2.9, 8. Evgeny Novikov (RUS/Ford Fiesta) 3.7, 9. Martin Prokop (CZE/Ford Fiesta) 6.3