This thesis examines how and why John Maynard Keynes’s policy proposals and economic theories were diffused in France between 1920 and the 1950s. Extant historiography has systematically asserted that Keynes’s writings had barely any impact in interwar France. In great part because of Keynes’s verdict on the Great War’s reparations and indictment of French foreign policy, particularly through his 1919 Economic Consequences of the Peace. The fact that Keynes was persona non grata in France has consequently also been used by historians to explain the belated acceptation of Keynes’s General Theory in that country. At the same time, though, it is commonly argued that France was one of the countries where Keynesianism became the most widespread after the Second World War, as a reaction to chronic economic underperforming in the 1930s and the war’s devastations. Based on an extensive perusal of archival and published sources, I advance, along twelve chapters, a starkly different hypothesis. For a start, I argue that in the 1920s Keynes’s ideas on reparations were significantly discussed in France. His audience was composed not only of detractors, but also of admirers from the Left and academia who helped him translate and publish his writings. The narrative then shifts towards analysing how Keynes’s estrangement from the majority of French public opinion started not with the issue of reparations, but with debates on monetary policy and the gold standard: beginning in the mid- 1920s and heightening during the Great Depression. Afterwards, I scrutinise how the translation and diffusion of the General Theory began taking place well before 1945; but also how Keynes’s theory continued to be resisted by a significant part of French economists even afterwards. And if Keynes’s economics did shape French anti-inflationary fiscal policy in post- Second World War reconstruction, their influence within the French state remained on the whole circumscribed. Consequently, this dissertation concludes that there was never a sweeping Keynesian revolution in France.