Riblon caught American Tejay van Garderen with about a mile left on the second ride up L'Alpe d'Huez, one of the Tour's most famed climbs.
Riblon threw his hands up and pumped his fists after clinching the second Tour stage win of his career. Van Garderen finished 59 seconds behind in second, and Italian Moreno Moser was 1:27 behind in third.
Froome, 3:18 back in seventh, extended his comfortable lead over his main rival, Alberto Contador, to more than 5 minutes with just three stages remaining. He is edging closer to becoming the second British rider to win the Tour, following Sky teammate Bradley Wiggins' success last year.
The 107-mile route from Gap to L'Alpe d'Huez featured two HC ascents — meaning they were so tough they were beyond classification, known as Hors Categorie — of L'Alpe d'Huez .
Contador was overtaken by Froome on the second ascent of L'Alpe d'Huez and finished 11th. The two-time former champion just held on to second place overall, now 5:11 behind Froome.
Colombian climber Nairo Quintana moved up to third overall and 21 seconds behind Contador.
With about eight miles to go on the last climb, Froome launched one of his trademark attacks. About a mile later, he attacked again and only Quintana could keep up with him as Contador dropped away.
But then Froome called for assistance with about two miles to go with what looked to be bike trouble. No team car could get up to help him because of fans in the way. So teammate Richie Porte gave him what looked like an energy bar to eat.
Fans jammed the 21 hairpin bends on L'Alpe d'Huez in a chaotic atmosphere. Many were in fancy costume, dressed as vicars, superheroes and other outfits of more dubious taste.
But there was still a degree of organization within the mayhem, with certain corners reserved for fans from certain countries.
One of those is known as "Dutch Corner," and several hundred screaming, shouting Dutch men and women formed a vortex that sucked the riders in amid a surreal cacophony of indecipherable shrieks, howls and wails.
Several dozen Norwegians, some in plastic Viking helmets, formed a human shield around one corner near the top. Elsewhere, a dozen or so Colombians marched uphill singing songs and carrying a giant national flag.
There were British Union Jack flags, Irish tricolors, Australian fans dressed in kangaroo suits and some dressed as inflatable giant flowers.
Occasionally, a distressed-looking police officer would blow a whistle, trying to stop fans from getting too close to the riders. One got too close to Riblon, who elbowed him in the chest to get him away, and a young boy ran in front of Froome.
Barricades were erected on the last part of the climb to give the riders some room.