The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. Its Constitution was drafted and adopted at the International Health Conference in New York from June 19 to July 22, 1946, signed by representatives of 51 UN members and 10 other nations, and entered into force on April 7, 1948, commemorated annually as World Health Day. WHO succeeded earlier bodies including the Health Organization of the League of Nations (1920), Office International d'Hygiène Publique (1907), and Pan-American Sanitary Bureau (1902), with work beginning in earnest in 1951 after resource infusions. Headquartered in Geneva, Switzerland (Avenue Appia 20, CH-1211 Geneva 27; Tel: +41 22 791 21 11), WHO operates through six regional offices (Africa in Brazzaville; Americas in Washington D.C.; Eastern Mediterranean in Cairo; Europe in Copenhagen; South-East Asia in New Delhi; Western Pacific in Manila) and 150 field offices worldwide. Only sovereign states are members. It coordinates international health responses, sets standards, provides technical assistance, and hosts conferences. Key contacts include media inquiries at mediainquiries@who.int and the website https://www.who.int/, with social media on Facebook (https://www.facebook.com/WHO), X/Twitter (@WHO), Instagram (@who), YouTube (http://www.youtube.com/who), and LinkedIn (https://www.linkedin.com/company/world-health-organization). Major initiatives and achievements include the Smallpox Eradication Program (1950s-1979, first disease eradicated by human effort, declared in 1979), Essential Medicines List (1978), Global Malaria Eradication Program (1955), Intensified Smallpox Eradication Program (1967), Global Polio Eradication Initiative (1988, reducing cases from over 125 countries), and responses to HIV/AIDS (since 1983 discovery), SARS (2003), and ongoing emergencies. Governance is led by the World Health Assembly (WHA) as the supreme decision-making body and the Executive Board for policy implementation. Funding comes from assessed contributions from members and voluntary contributions, including a recent US$10M grant from the Islamic Development Bank on December 12, 2024.