Founded in 1919 as part of the League of Nations, the International Labor Organization (ILO) is the only surviving creation of the Treaty of Versailles. Headquartered in Geneva, the ILO became the first agency of the United Nations in 1946. Through international action and by bringing together representatives of government, employers, and labor, the organization formulates international labor standards, aiming to establish basic labor rights such as a prohibition on forced labor; the right to organize; the right to bargain collectively; and the right to equal opportunity across ethnic, racial, and gender differences, as well as on such matters as regulation of hours of work, provision of adequate wages, protection of workers against occupational disease and injury, and protection of women and children. Western powers founded the ILO with the goal of diffusing the appeal of Bolshevism and harnessing the wartime loyalties of labor movements to a reformist internationalism; they also emphasized the practical importance of multilateral cooperation in the arena of labor reform, sweated labor in one country endangered decent labor standards among its competitors.

The United States, which never joined the League of Nations, did not join the ILO until 1934. However, Samuel Gompers, head of the American Federation of Labor, chaired the Labor Commission created by the 1919 Peace Conference to draft the ILO Constitution, which established the "tripartite" principle of organization that remains the ILO's cornerstone. Under tripartism which makes the ILO unique among the UN and other international agencies, not only governments, but also workers and employers are represented (in a 2:1:1 ratio) in the ILO. Tripartism proved the heart of U.S.-ILO tensions from the early 1950s through 1977, when the United States withdrew from the ILO. Interpreting tripartism to mean independent workers' and employers' representatives, the United States complained that Soviet, Eastern European, and some Third World union and employers' representatives were voting on government instructions.

Another source of controversy lay in the ILO's expanding agenda from traditional labor standards to broader questions of political economy, full employment, development policies, and human rights concerns which flowed from the increasing proportion of Third World nations among ILO members. The United States objected, partly on ideological grounds, partly because its representatives believed that the changes distracted the organization from its traditional focus upon verifiable commitments to specific rights and freedoms. Injured by the loss of U.S. dues, which accounted for one-quarter of the organization's budget, the ILO trimmed its sails, and the United States rejoined in 1980.

At the end of the twentieth century, the ILO enjoyed membership from over 160 nations, and had concluded 183 conventions. The ILO's main enforcement mechanism was publicity the organization's stately hearings and reports continued to expose member nations' labor laws and practices to scrutiny. The need for international labor standards was never greater than in the era of "globalization," and the ILO's strongest supporters continue to lament the absence of stronger means of enforcement.

The ILO consists of a general conference of representatives of the members (four from each member state—two from the government, an employer, and a worker) that meets once a year, a governing body of 56 people (28 representing governments, 14 employers, and 14 labor) that meets three times a year, and an International Labor Office controlled by the governing body. The ILO is financed by contributions from member states; 182 countries belong to the organization.