The system

International organisations

21 organisations, and every member state of each — resolved against this site’s own list of 193 UN member states rather than taken on trust.

Why these

African Union

Every state on the continent belongs -- the only regional organisation with a claim to full coverage of its geography, successor to the OAU of 1963.

Caribbean Community

The Caribbean's community and single market -- fifteen full members, a shared court of last resort for some, and free movement for all.

Commonwealth of Nations

A voluntary association of 56 states, most with a shared imperial past and several -- Mozambique, Rwanda, Gabon, Togo -- with none, which is the interesting part.

Council of Europe

Europe's human-rights organisation -- older and wider than the EU, and custodian of the European Convention on Human Rights and its court.

Economic Community of West African States

West Africa's economic community and its crisis responder -- reduced from fifteen members to twelve when Burkina Faso, Mali and Niger withdrew in January 2025.

European Union

The most deeply integrated regional organisation, and the one that publishes the most about itself -- its documents are reusable under Decision 2011/833/EU, which almost no other organisation matches.

International Bank for Reconstruction and Development

The World Bank's founding institution: membership requires joining the IMF first, and 189 states have.

International Telecommunication Union

The oldest organisation in the UN system -- founded in 1865 for the telegraph -- and the registry through which states share spectrum, orbital slots and numbering.

League of Arab States

Founded in Cairo in March 1945, months before the UN itself, and the body through which the Arab states coordinate.

North Atlantic Treaty Organization

The Atlantic alliance of 1949, whose Article 5 makes an armed attack on one an attack on all -- 32 members since Sweden acceded in 2024.

Organisation for Economic Co-operation and Development

The industrialised economies' policy club, whose 38 members are the closest thing 'developed country' has to a definition with a list.

Organisation of Islamic Cooperation

The largest intergovernmental organisation after the UN itself: 57 member states across four continents.

Organization for Security and Co-operation in Europe

The broadest security organisation there is: 57 participating States from Vancouver to Vladivostok, grown out of the Helsinki Final Act.

Organization of American States

The Americas' regional organisation under Chapter VIII of the UN Charter, seating 35 states of the hemisphere.

Southern African Development Community

Southern Africa's development community: sixteen states from the DR Congo to the Indian Ocean islands.

United Nations

The organisation this site was built to document: 193 member states, and the only one with near-universal membership.

United Nations Educational, Scientific and Cultural Organization

The UN's education, science and culture agency, whose membership has never quite matched the UN's: states have joined it first, left it in protest, and rejoined decades later.

Universal Postal Union

The postal union of 1874, the UN system's second-oldest body, through which every national post reaches every other.

World Health Organization

The UN's health agency, and a membership broader than the UN's own: states coordinate on disease through it that meet nowhere else.

World Meteorological Organization

The weather agency. An observation network is only as good as its least-connected member, which is why its membership reaches past states to the territories that run their own meteorological services.

World Trade Organization

Not a UN body: the trade system's own organisation, successor to the GATT, where accession is negotiated case by case and has taken some states decades.

Compiled from Wikidata, which is CC0. Membership is resolved by name against the member-state spine, never asserted from the query: the filter that makes one organisation’s count correct makes another’s wrong, and both modellings are defensible.