Oskar Ryszard Lange was a Polish economist and diplomat. He is best known for advocating the use of market pricing tools in socialist systems and providing a model of market socialism. He responded to the economic calculation problem proposed by Ludwig von Mises and Friedrich Hayek by claiming that managers in a centrally-planned economy would be able to monitor supply and demand through increases and declines in inventories of goods, and advocated the nationalization of major industries. During his stay in the United States, Lange was an academic teacher and researcher in mathematical economics. Later in socialist Poland, he was a member of the Central Committee of the Polish United Workers' Party.

Market socialism is a type of economic system involving social ownership of the means of production within the framework of a market economy. Various models for such a system exist, usually involving cooperative enterprises and sometimes a mix that includes public or private enterprises. In contrast to the majority of historic socialist economies, which have substituted the market mechanism for some form of economic planning, market socialists wish to retain the use of supply and demand signals to guide the allocation of capital goods and the means of production. Under such a system, depending on whether socially owned firms are state-owned or operated as worker cooperatives, profits may variously be used to directly remunerate employees, accrue to society at large as the source of public finance, or be distributed amongst the population in a social dividend.