The Spaniard's fifth victory in 10 races was his most crushing of the season and stretched his overall lead to 24 points after McLaren's [ Images ] Kimi Raikkonen [ Images ], his closest rival, finished second.
With an army of blue and yellow-shirted fans cheering him on under clear blue skies, Alonso crossed the line with his hand up in a 'High Five' as the carmaker celebrated a first home win as a constructor for 22 years.
"It was really, really good. The car performed extremely well again in the race, we were very competitive from the first lap," said Alonso.
"The last 10 laps went really slowly. I just wanted to cross the line and enjoy the victory with the team and the grandstand opposite the pits where most of the people were coming from the Renault factory."
The 23-year-old lapped all but two cars to end a Schumacher stranglehold as the first winner in five years from outside the German family.
"I'm a bit disappointed really," said Raikkonen, who had started 13th after a blown engine in Friday practice incurred a 10 place penalty on the grid. "What happened on Friday destroyed the whole weekend completely.
"I only dropped two points, so it didn't cost too much, but I want to win races."
Alonso has 69 points to Raikkonen's 45. Schumacher has 40. Renault stayed ahead in the constructors' standings with 89 points to McLaren's 71.
Both Button and Trulli benefited from Italian Giancarlo Fisichella's [ Images ] misfortune, Alonso's team mate stalling his Renault on his final pitstop after challenging Schumacher.
Fisichella was sixth, ahead of Toyota's Ralf Schumacher. Canadian Jacques Villeneuve took the final point for Sauber.
Alonso made a clean start from pole position and ran in isolation for lap after lap as Trulli, holding on to second place from the front row, held up Ferrari's Schumacher and the rest of the field.
"I spent 18 laps behind him and losing quite a bit of time," said Schumacher.
"It was all with traffic so to finish third is okay."
With 15 laps gone, Alonso was 21 seconds clear and had a big enough buffer to pit comfortably five laps later and rejoin in the lead.
The McLarens had by then been unleashed, Trulli pitting with Schumacher at the end of lap 18 and the German coming out ahead of the Italian.
Colombian Juan Pablo Montoya [ Images ] closed to within eight seconds of Alonso before pitting and allowing team mate Raikkonen to take over in second place. Montoya eventually retired after 48 of the 70 laps with a suspected hydraulic problem.
Alonso, who had not scored points in the last two races after crashing in Canada [ Images ] and then being unable to compete in Indianapolis due to the Michelin tyre crisis that sidelined seven of the 10 teams, was not to be threatened.
With Renault's new president Carlos Ghosn attending his first Grand Prix, the Spaniard took the chequered flag 11.8 seconds clear of Raikkonen.
It was the first time Renault had won a French Grand Prix as a constructor at Magny-Cours. Their last win, in the turbo era, was at Le Castellet with four times champion Alain Prost in 1983.
That was some consolation for organisers of what was also the first French Grand Prix since 1965 without a French driver competing, even if Prost did appear on the podium to hand Alonso his trophy.
Michelin could also breathe a sigh of relief after Indianapolis, cars with their tyres filling eight of the top 10 places with the French company claiming a ninth win of the year.