The document is signed and sealed by Cardinal Joseph Fesch, who presided over the clandestine wedding that took place at the behest of Pope Pius VII as a condition for his presence at Napoleon's coronation.
It is part of a collection being auctioned off by US billionaire and francophile Christopher Forbes that mainly comprises artefacts from the reign of Napoleon's nephew and heir, Napoleon III.
Cardinal Fesch, as France's ambassador to Rome, negotiated the pope's participation in Napoleon's grandiose coronation in Notre Dame Cathedral when he famously crowned himself on December 2nd, 1804.
The pope had refused to officiate at the coronation unless Napoleon and Josephine underwent the Catholic wedding rite, and the emperor-to-be agreed to it in order to avoid a scandal.
Cardinal Fesch secretly performed the ceremony at the Tuileries palace chapel on December 1st, 1804.
Napoleon Bonaparte was initially smitten by Josephine de Beauharnais, whom he described as “worse than beautiful”, but the marriage did not survive their frequent separations while he was leading his various campaigns to conquer Europe.
The marriage was annulled in 1810, after the couple failed to have children.
Osenat has not yet stated a value for the religious marriage certificate, but it sold the civil document for €437,000 in 2014.
Forbes, a frequent presence at exclusive auctions, could have sold the collection in New York or London, but instead chose the Osenat auction house which specialises in France's First and Second Empires.
Osenat is based in Fontainebleau, south of Paris, the seat of French monarchs from the medieval Louis VII to Napoleon III, who reigned from 1852 to 1870.
Forbes is also selling some 1,300 letters or manuscripts of Napoleon III, his consort Eugenie and their son the imperial prince.
Some 500 paintings include portraits of Napoleon III and Eugenie by German painter Franz Xaver Winterhalter, Europe's premier court portraitist at the time.
The French government has a “right of pre-emption” enabling it to purchase items that it deems should remain in France. The estimated value of the collection and individual items has not been given.
Forbes, who maintains a chateau in Normandy and founded the American Friends of the Louvre, developed his passion for Napoleon III after his father offered him a portrait of the emperor when he was 16.
A preview of selected items to be sold by Osenat will be shown February 23rd at the Opera Garnier in Paris.