Mousnier was born in Paris and received his education at the École pratique des hautes études.

[1] Mousnier was one of the few post-war French historians who was neither a member of the Annales School, or a subscriber to Marxist views of history.

A right-wing Roman Catholic, Mousnier had a famous feud with the Soviet Marxist historian Boris Porchnev over whether peasant revolts in 17th-century France were a function of class struggle; he argued since the concept of class was largely unknown in that period, Porchnev was wrong to identify it as a driver.

In Mousnier's view, social classes did not emerge as an important factor in French society until the 18th century, with the coming of a more market-oriented economy.

Mousnier made it his life work to study how the relationships between different orders operated through networks of patronage.