The World Health Organization (WHO) is a specialized agency of the United Nations (UN) that acts as a coordinating authority on international public health. Established on 7 April 1948, and headquartered in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health Organization, which had been an agency of the League of Nations.

The WHO's constitution states that its objective "is the attainment by all peoples of the highest possible level of health." Its major task is to combat disease, especially key infectious diseases, and to promote the general health of the people of the world.

The World Health Organization (WHO) is one of the original agencies of the United Nations, its constitution formally coming into force on the first World Health Day, (7 April 1948), when it was ratified by the 26th member state. Prior to this its operations, as well as the remaining activities of the League of Nations Health Organization, were under the control of an Interim Commission following an International Health Conference in the summer of 1946. The transfer was authorized by a Resolution of the General Assembly. The epidemiological service of the French Office International d'Hygiène Publique was incorporated into the Interim Commission of the World Health Organization on 1 January 1947.