American economist who became the foremost authority on U.S. labour in the first third of the 20th century.

Commons studied at Oberlin College and at Johns Hopkins University and taught at the University of Wisconsin (1904–32). He established his reputation with the publication of A Documentary History of American Industrial Society, 10 vol. (1910–11), and History of Labour in the United States, 4 vol. (1918–35). Commons's theory of the evolution of the American labour movement in terms of changes in the market structure was generally accepted. After World War I, Commons broadened his reputation with the publication of Legal Foundations of Capitalism (1924) and its sequel, Institutional Economics (1934).

Commons drafted much of the reform legislation that made Wisconsin an example for other states. Such legislation introduced legal privileges for labour unions, compulsory unemployment insurance, compulsory workers' compensation, and government regulation of utilities. He also made notable contributions to the federal government in the areas of civil service, public utilities, and unemployment insurance and contributed to the design of the Social Security Act of 1935, the U.S. government's first comprehensive program to fund old-age benefits through payroll taxes.