North Atlantic Treaty Organization
Security · NATO
Fourteen articles signed in Washington on 4 April 1949 are the whole of the agreement. Article 5 treats an armed attack on one party as an attack on all, and it has been invoked once, on 12 September 2001. Article 6 fixes where that cover reaches: territory in Europe or North America, and islands in the North Atlantic north of the Tropic of Cancer.
32 countries
- AlbaniaThe 2023 census counted 2,402,113 people in Albania and the voter roll of April 2025 held 3,713,761 names. The land, the history and the economy, each figure dated.
- Belgium11.8 million people on 30,688 square kilometres, three official languages and six governments. A federal structure built around a language border, and 16 heritage sites.
- BulgariaFounded by treaty in 681 and rebuilt by another in 1878, Bulgaria is a country of 6.4 million in the eastern Balkans, in the EU since 2007 and the euro since 2026.
- Canada
- CroatiaCroatia counted 3,871,833 residents in 2021, 9.64% fewer than in 2011, and registered 94.8 million tourist nights in 2025, 94.3% of them on the Adriatic.
- Czechia10.9 million people on 78,871 landlocked square kilometres. A state created by negotiation in 1993, an industrial economy tied to Germany, and 17 World Heritage properties.
- Denmark5.8 million people on 42,925 square kilometres of peninsula and islands, highest point 171 metres. A 179-seat parliament, four of whose seats sit in the Arctic.
- EstoniaA Baltic republic of 1,369,995 people as of 1 January 2025 whose statehood survived occupation as a legal record, and whose voting and company registry now run the same way.
- Finland5.7 million people on 390,905 square kilometres of forest and lake. Independent since 1917, in the EU since 1995, and in NATO since April 2023.
- France68.6 million people and 643,801 square kilometres across three oceans. Five republics since 1789, 56 nuclear reactors, and public debt at 115.5% of output.
- Germany83.6 million people on 357,588 square kilometres with nine land borders. A constitution written to be temporary in 1949, and an export economy that grew 0.2% in 2025.
- Greece10.6 million people on 131,957 square kilometres of mountain and archipelago. A state founded in 1821, a constitution from 1975, and 21 World Heritage properties.
- Hungary9.5 million people on 93,030 landlocked square kilometres with seven neighbours. A treaty in 1920 took 72% of the territory, and the question has never closed.
- IcelandAn empty island claimed in sixty years and written down as it happened: 376,248 people counted in 2022, on crust the Mid-Atlantic Ridge pulls apart by 19 millimetres a year.
- ItalyItaly holds about 58.9 million people, was proclaimed a single state on 17 March 1861 and became a republic in 1946. Its cities, regions and districts still do the work.
- LatviaLatvia holds 1,845,096 people as of 1 January 2026 on flat, wet ground on the Baltic, under a constitution of 1922 restored in 1991 after two rewritings of its population.
- LithuaniaThree ultimatums between 1938 and 1940 ended Lithuania's first republic. The state restored on 11 March 1990 has spent since then rearranging its connections westward.
- Luxembourg681,973 residents in 2025, 47% of them foreign nationals, and 223,000 more crossing a border to work. A grand duchy of 2,586 square kilometres with three languages and 8.2 trillion euros of fund assets.
- Montenegro617,213 people in 2022 on 13,883 square kilometres. A state named for a mountain above Kotor that reached the sea in 1878 and now earns much of its living there.
- Netherlands17.9 million people on 42,201 km2, a fifth of it water and much of the rest below sea level. What the Dutch earn from, how they are governed and what there is to see.
- North Macedonia1,836,713 people counted in 2021, a name agreed with Greece in 2018, EU talks tied to Bulgaria, and exports led by development zones that shipped €3.18bn in 2025.
- NorwayA Nordic monarchy of 5.6 million that wrote its constitution before it was independent and claimed its seabed six years before anyone found oil under it.
- Poland37.5 million people between the Baltic and the Carpathians. A state that vanished for 123 years, moved west after 1945, and now runs the EU's most coal-dependent grid.
- Portugal10.3 million people on 92,225 km2, a language spoken by 250 million, a border unchanged since the 13th century, and close to three foreign visitors a year for every resident.
- RomaniaA country of 19 million on the lower Danube, made in 1859 out of a gap in a treaty, enlarged in 1918, cut apart in 1940, and in the European Union since 2007.
- SlovakiaA landlocked Central European country of five and a half million, independent since 1993, whose four car plants built 1,040,000 vehicles in 2016.
- SloveniaA Central European country of 2,133,852 people as of October 2025, independent since 1991, with borders drawn by other people's treaties and a state its voters authorised.
- Spain48.6 million people on 505,990 km2, five official languages, seventeen governments and 97 million visitors a year. What Spain is, how it is run and what is worth seeing.
- Sweden10.6 million people on 528,861 square kilometres from the Baltic to the Arctic. A monarchy whose 1974 constitution left the crown no power, and which kept its own currency.
- Türkiye85.4 million people at the end of 2023, a capital, alphabet, clock and English name each fixed by statute, on a plate driven west between two faults.
- United Kingdom67.3 million people across four countries on 242,495 square kilometres. An uncodified constitution, an economy four fifths services, and 35 World Heritage properties.
- United StatesEstados Unidus
Common questions
Questions about NATO
Which countries are in NATO?
The 32 parties to the North Atlantic Treaty are listed on this page. Twelve governments signed at Washington on 4 April 1949: Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, the Netherlands, Norway, Portugal, the United Kingdom and the United States. The rest acceded in ten later rounds, the most recent of them Sweden on 7 March 2024.
What does Article 5 actually say, and how often has it been used?
It provides that an armed attack on one or more parties in Europe or North America is to be considered an attack on all, and that each party will assist the party attacked by taking such action as it deems necessary, including the use of armed force. The choice of action stays with each government. The Council invoked it on the evening of 12 September 2001 and has not done so before or since.
Can a country outside Europe join NATO?
Not on the treaty's own words. Article 10 allows the parties to invite any other European State in a position to further the principles of the treaty and to contribute to the security of the North Atlantic area. Canada and the United States are parties because they signed in 1949 rather than acceded, so the accession rule has never applied to them.
How does a country actually join?
By unanimous invitation and then by deposit. Accession talks are held at the alliance's headquarters, the invitee sends a letter of intent, the members sign an accession protocol and each ratifies it under its own national procedure, and the state becomes a party when it deposits its instrument of accession with the Government of the United States, which holds the treaty. Finland deposited on 4 April 2023 and Sweden on 7 March 2024.
Can a member leave?
Article 13 provides for it. Twenty years after the treaty came into force, which is to say from 24 August 1969 onwards, any party may cease to be a party one year after giving notice of denunciation to the Government of the United States, which then informs the others. France withdrew from the integrated military structure in 1966 without leaving the treaty, and announced full participation again in April 2009.
Is NATO the same thing as the European Union?
No. They are separate organisations founded on separate treaties, and the two lists do not match. Austria, Cyprus, Ireland and Malta are members of the Union and are not parties to the North Atlantic Treaty; Albania, Canada, Iceland, Montenegro, North Macedonia, Norway, Türkiye, the United Kingdom and the United States are parties to it and are not members of the Union.
Sources
- The North Atlantic Treaty, Washington D.C., 4 April 1949 · NATO. The official text and its footnotes: Articles 5, 6, 10, 13 and 14, the entry into force on 24 August 1949, the protocol of 22 October 1951 and the note of 16 January 1963 on the Algerian departments.
- NATO member countries · NATO. The twelve founding signatories, the date of each accession, the position of Iceland without armed forces and the French withdrawal from the integrated military structure in 1966.
- Enlargement and Article 10 · NATO. The accession procedure step by step, the ten rounds of enlargement, the declared aspirants and the Bucharest decision of April 2008.
- Collective defence and Article 5 · NATO. The single invocation of Article 5, the Council statement of 12 September 2001 and the distinction from consultation under Article 4.
- Consensus decision-making at NATO · NATO. That no vote is taken at any level of the organisation and that every decision is a collective decision of the member countries.
- The Hague Summit Declaration, 25 June 2025 · NATO. The commitment to 5% of GDP a year by 2035, its split into at least 3.5% and up to 1.5%, and the review set for 2029.