The 30-year-old sprinter, who snatched his best career wins in the Tour de France, showed he still had some speed left in his legs by surging with more than 200 metres to go to outsprint the field in Buzancais, in the Loire valley.
Briton David Millar, winner of Sunday's prologue near Paris, retained his overall lead with a one-second edge over young Czech Roman Kreuzinger.
"Prestigious victories? I've had my share before but I wanted this badly because it's been a long time since the last," Nazon said.
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"This is great for confidence so early in the season and I hope to be able to win more on this Paris-Nice," added the AG2R rider.
His early move allowed him to beat German Sebastian Siedler and Australia's Matthew Hayman, while pre-race favourite Daniele Bennati of Italy was fourth.
Former world champion Tom Boonen of Belgium, hampered by a bad cold, was a disappointing eighth. The Quick Step team leader had won the first two stages of Paris-Nice in its two previous editions.
Nazon's biggest victory to date was in the last stage of the Tour de France on the Champs-Elysees in 2003.
"Obviously I hope to be on the Tour de France once more this summer, but a lot can happen beforehand. I can crash or be sick," he said.
"Today, I surged very early with more than 200 metres to go and I was surprised no one followed suit. I held as long as I could and fortunately I made it," he added.
The stage was marked by a long breakaway, launched from the gun by three Frenchmen, under-23 world championship silver-medallist Romain Feillu, Christophe Laurent and Herve Duclos-Lassalle, and a Spaniard, Ivan Velasco.
The four held a maximum lead of 10:30 after 70 km before the bunch reacted. They were caught with two km left on the flat and sunny stage.
A minute's silence was observed at the start in memory of Kazakh rider Andrei Kivilev, killed in a crash on the race exactly four years ago.
Team chiefs also staged a silent protest against the decision by the magistrate in charge of the 'Puerto' doping scandal to drop the case on grounds that the evidence gathered was not an offence at the time according to Spanish law.
The teams' union AIGCP asked for "justice to prevail" saying the case had harmed cycling.
German Jan Ullrich and Italian Ivan Basso were among several riders withdrawn from last year's Tour de France after being cited in the case.
Tuesday's second stage takes the 160 riders from Vatan to Limoges over 177 km.
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