Jean Charles Léonard de Sismondi (also known as Jean Charles Leonard Simonde de Sismondi) (French: [ʒɑ̃ ʃaʁl leɔnaʁ də sismɔ̃di]; 9 May 1773 – 25 June 1842),[1] whose real name was Simonde, was a historian and political economist, who is best known for his works on French and Italian history, and his economic ideas. His Nouveaux principes d'économie politique, ou de la richesse dans ses rapports avec la population (1819) represents the first liberal critique of laissez-faire economics.[2][3] He was one of the pioneering advocates of unemployment insurance, sickness benefits, a progressive tax, regulation of working hours, and a pension scheme.[4][5] He was also the first to coin the term proletariat to refer to the working class created under capitalism,[4][6] and his discussion of mieux value anticipates the Marxist concept of surplus value.[7][8] According to Gareth Stedman Jones, "much of what Sismondi wrote became part of the standard repertoire of socialist criticism of modern industry."[9][better source needed]

In 1913, Rosa Luxemburg wrote a critique of Sismondi in The Accumulation of Capital.[24]