Marcel Cachin (20 September 1869 – 12 February 1958) was a French Communist politician and editor of the daily newspaper L'Humanite.

In 1905, he joined the new French Section of the Workers' International (SFIO) and won election to the Chamber of Deputies representing the Seine in 1914.

On that occasion he strongly supported Kerensky's Provisional Government, which was pledged to continue Russia's participation in World War I, and denounced Lenin and the Bolsheviks.

However, following the end of the war, there was a leftward shift among Cachin's grassroots supporters and a growing sympathy for the October Revolution.

As a strong supporter of the pro-Soviet Communist Party, he refused to disavow the Molotov–Ribbentrop Pact and was removed from elected office in 1940.