Born Aug. 18, 1879, in London; died Dec. 12, 1950, in Alfortville. Active figure in the French workers movement. Son of C. Longuet and J. Marx. Doctor by profession. Supporter of the Guesdist tendency in the French socialist movement.
In 1905, Longuet joined the Socialist Party. In 1937 he left the Socialist Party, protesting the political line of its leadership. In 1938 he joined the Communist Party, in which he was an active figure.