The United Nations Industrial Development Organization (UNIDO) (French: Organisation des Nations unies pour le développement industriel; French/Spanish acronym: ONUDI) is a specialized agency of the United Nations that assists countries in economic and industrial development. It is headquartered at the UN Office in Vienna, Austria, with a permanent presence in over 60 countries. As of April 2019, UNIDO comprises 170 member states, which together set the organization's policies, programs, and principles through the biannual General Conference.

UNIDO was established in 1966 by the UN General Assembly to promote and accelerate the industrialization of developing countries, which were emerging from decolonization in record numbers and with little to no industrial base. In 1979 it became one of the 15 specialized agencies of the UN, with its new constitution coming into force in 1985. Since its founding, the organization has restructured and reformed several times; the 2013 Lima Declaration expanded its mission to include promoting "inclusive and sustainable industrial development" (ISID), defined as benefiting greater numbers of people while safeguarding the environment. UNIDO is a member of the United Nations Development Group, a coalition of UN entities aimed at fulfilling the Sustainable Development Goals.

On 25 July 2016, the United Nations General Assembly adopted Resolution A/RES/70/293, proclaiming the period 2016-2025 as the Third Industrial Development Decade for Africa (IDDA III). UNIDO was called upon to lead the initiative in collaboration with a range of partners. These include the African Union Commission, the New Partnership for Africa’s Development, the Economic Commission for Africa, etc.

From 2018 to 2021, UNIDO's strategic priorities include creating shared prosperity; advancing economic competitiveness; safeguarding the environment; and strengthening knowledge and institutions. Each of these goals is to be achieved through technical cooperation, policy advice, analysis and research, the development of uniform standards and quality control, and partnerships for knowledge transfer, networking and industrial cooperation.

UNIDO employs some 670 staff and draws on the services of some 2,800 international and national experts—approximately half from developing countries—annually, who work in project assignments throughout the world.