The International Refugee Organization (IRO) was an intergovernmental organization founded on 20 April 1946 to deal with the massive refugee problem created by World War II. A Preparatory Commission began operations fourteen months previously. In 1948, the treaty establishing the IRO formally entered into force and the IRO became a United Nations specialized agency. The IRO assumed most of the functions of the earlier United Nations Relief and Rehabilitation Administration. In 1952, operations of the IRO ceased, and it was replaced by the Office of the United Nations High Commissioner for Refugees (UNHCR).
The Constitution of the International Refugee Organization, adopted by the United Nations General Assembly on 15 December 1946, is the founding document of the IRO. The constitution specified the organization's field of operations. Controversially, the constitution defined "persons of German ethnic origin" who had been expelled, or were to be expelled from their countries of birth