Russia's Rosoboronexport military corporation and DCNS, the warships' French maker, signed the contract on the sidelines of the Saint Petersburg Economic Forum.
French Foreign Trade Minister Pierre Lellouche, who was present along with Russian President Dmitry Medvedev, estimated the contract at 1.12 billion euros.
Rosoboronexport director Anatoly Isaikin added that France had agreed to transfer sensitive technologies, a Russian demand which prolonged negotiations.
Russia has been keen to receive an advance naval operating system called Senit-9 from France as part of the package.
Isaikin said that, although the first two ships would be built in France, a third and fourth should be bought and would be built in Russia. He could give no date for that part of the project.
French President Nicolas Sarkozy welcomed the agreement, saying it was evidence of strategic cooperation between the two countries.
A Mistral-class ship can carry up to 16 helicopters, four landing craft, 13 battle tanks, around 100 other vehicles and a 450-strong force. It has facilities for a full command staff and is equipped with a 69-bed hospital.
Russia’s Prime Minister Vladimir Putin is to meet Sarkozy and Prime Minister François Fillon next week after attending the opening of the Le Bourget air show on Monday.