The World Health Organization (WHO) is a specialized agency of the United Nations (UN), established as an international institution to direct and coordinate global health matters. Its objective, enshrined in its Constitution, is "the attainment by all peoples of the highest possible level of health". The WHO was founded on 7 April 1948, formally beginning its work on 1 September 1948, to address the common danger posed by unequal development in the control of diseases, especially communicable diseases. It inherited the duties of the League of Nations' Health Organization and the Paris-based Office International d'Hygiène Publique.
The mechanism of the WHO is governed by the World Health Assembly (WHA), its decision-making body composed of 194 Member States. Under Article 2 of its Constitution, its functions include acting as the directing and co-ordinating authority on international health work, assisting governments in strengthening health services, and stimulating work to eradicate epidemic and endemic diseases. The WHO connects directly to the International Health Regulations (IHR), a legally binding instrument that guides its Member States on their obligations concerning public health risks.
The organization has undergone significant recent change following the COVID-19 pandemic. In 2024, the Seventy-seventh World Health Assembly adopted amendments to the IHR. These amendments introduced a new level of global alert called a "pandemic emergency" to trigger stronger international collaboration, and established a Coordinating Financial Mechanism to support low- and middle-income countries. Additionally, Member States adopted the WHO Pandemic Agreement in 2025 to improve global preparedness and response to future pandemics.