The ride along four small hills took the pack 222.5 kilometres (138 miles) from Blagnac to Brive-la-Gaillarde, seen as a transitional stage before Saturday's time trial.
Wiggins, Cavendish and the Sky team made it look easy with an almost textbook sprint setup. With about 1.3 kilometres left, Wiggins - rare for a yellow-jersey holder - took the head of the pack and chased down six breakaway riders, then peeled away with about a kilometre to go.
The Sky train motored ahead and Cavendish, showing he's perhaps the world's most explosive rider, whirred around the remaining escapees in the last few hundred meters to win by a couple of bike lengths.
Luis Leon Sanchez, seeing Cavendish speed by, appeared to sigh with resignation at the Briton's velocity. By the end, Cavendish beat Matt Goss of Australia in second and Peter Sagan of Slovakia in third.
Cavendish, who has been largely overshadowed on Sky by Wiggins, collected his second stage win of this Tour and his 22nd career Tour stage victory - the same number as seven-time champion Lance Armstrong.
"I just used the slipstreams," said Cavendish. "I have used this technique to win 22 stages ... it's a magic number - there's one more to go."
Wiggins and Cavendish shared a long hug after the finish.
"It was dangerous in the final. This morning we decided to put the train in place and help Mark in the final," Wiggins said. "It's my gift to him."
With 14 of 22 teams competing this year without a stage win yet, the day's ride got off to a furious pace with riders looking for momentary glory by breaking away. But the pack held close, never letting the escapees more than about 3-1/2 minutes ahead.
Shortly after the halfway mark, several riders including Belgian star Philippe Gilbert and Denis Menchov of Russia crashed after a large dog crossed the road in front of the pack. Gilbert barked at the dog's owners on the roadside, but was held back by a BMC team manager.
After yo-yoing attacks on the peloton, Wiggins and Sky teammate Edvald Boasson Hagen gave a playbook — if a bit early — leadout to the sprint specialist, and Cavendish showed his domination at the end.
"And once again he showed, if there was any doubt, that he is the fastest man in the world," Wiggins said.
After Cavendish's bunch, the Sky leader finished four seconds later in a 30-rider group that included his biggest rivals for the Tour title.
The top standings didn't change. Overall, Wiggins has a lead of 2 minutes and 5 seconds over Sky teammate Christopher Froome, in second. Italy's Vincenzo Nibali was third, 2:41 behind. Defending champion Cadel Evans of Australia was sixth, 9:57 back.
Friday's victory gives Britain five stage wins this year from four different riders — Cavendish, Froome, Wiggins and David Millar. That's the same number of wins for riders from France.
"For the British, it's a really big day," said French President Francois Hollande, visiting at the finish line in Brive-la-Gaillarde, a town in his political home base.
The final big showdown comes on Saturday in the 53.5-kilometre (33-mile) time trial from Bonneval to Chartres. Riders will leave one-by-one from a ramp in the race against the clock, in reverse order of the standings.
Greg Keller and Samuel Petrequin in Brive-la-Gaillarde contributed to this report.