The vessels are scheduled for delivery to the Italian-Swiss company in 2025 and 2027.
MSC has also signed a preliminary deal for a further investment in LNG that could be worth another four billion euros.
French prime minister Edouard Philippe hailed the contrat as excellent news not only for the 3,200 employees at Chantiers but also the economy and the environment.
"It's good for the men and women who work with les Chantiers - the sub contractors and the manufacturers," said Philippe. "It's also good for Saint-Nazaire, the region around it and for France.
Idea
"The deal shows MSC's desire to move away from traditional modes of propulsion to new ones such as liquid natural gas."
"The direct and indirect fallout of the deal for the French economy will be substantial, " said Pierfrancesco Vago, head of MSC's cruise liner division. "It shows how far ahead France in the sphere of sustainable technologies for the maritme industry."
