Conceived by British architect Norman Foster, the slender white viaduct in the picturesque Tarn valley will provide a new motorway link between Paris and the Spanish border, easing congestion in the Rhone valley during the busy summer months.
Chirac unveiled a simple commemorative plaque before plunging into a throng of white-helmeted construction workers, as an air-display team flew past the bridge trailing red, white and blue smoke - the colours of the national flag.
The highest of the bridge's seven concrete pillars stands at 343m, 19m higher than the Eiffel Tower. At almost 2.5km, it is longer than the famous Champs Elysees avenue in Paris and slightly curved to afford drivers a dramatic view of the surrounding countryside and the ancient town of Millau with its mediaeval bell tower.
"The whole thing looks impossibly delicate," Foster said. Describing it as a "sculpture in the landscape", Foster's creation cost a 394 million euro ($523 million) and was financed by construction firm Eiffage.
"It is a dialogue between nature and the man-made," he said.
The engineering feat has drawn rapturous praise for its elegant lines, which allow it to blend seamlessly into the surrounding region, famed for its gorges, mediaeval villages and Roquefort cheese.
The bridge is designed to end
traffic jams in the Tarn valley
"We were attracted by the elegance and logic of a structure that would march across the heroic landscape and in the most minimal way connect one plateau to the other," Foster, who also designed the German parliament's Reichstag building in Berlin, said.
"We were driven by the scale of the idea and the shared passion for the poetic dimension of engineering and its sculptural potential."
The Millau viaduct has drawn thousands of visitors since construction was started exactly three years ago.
The bridge will open to traffic at midnight on Friday and is expected to channel an average of 10,000 vehicles a day, with peaks of 25,000 during the summer holidays.
Eiffage will charge a toll of 4.60 euros in the low season and 6.50 euros in July and August for cars using the bridge, part of the A75 motorway linking the cities of Clermont-Ferrand to Beziers. Lorries will pay 19 euros.
Eiffage has a 75-year concession to operate the viaduct and has guaranteed the structure for 120 years.