As of October 2023, there are 31 member countries in NATO. These countries are sovereign states that come together through NATO to discuss political and security issues and make collective decisions by consensus. The 12 founding member countries of NATO are Belgium, Canada, Denmark, France, Iceland, Italy, Luxembourg, Netherlands, Norway, Portugal, the United Kingdom, and the United States. Since then, 19 more countries have joined NATO through nine rounds of enlargement (in 1952, 1955, 1982, 1999, 2004, 2009, 2017, 2020, and 2023) . The most recent country to join NATO is Finland, which became a member in April 2023. The 31 NATO member countries are:

1. Albania
2. Belgium
3. Bulgaria
4. Canada
5. Croatia
6. Czech Republic
7. Denmark
8. Estonia
9. Finland
10. France
11. Germany
12. Greece
13. Hungary
14. Iceland
15. Italy
16. Latvia
17. Lithuania
18. Luxembourg
19. Montenegro
20. Netherlands
21. North Macedonia
22. Norway
23. Poland
24. Portugal
25. Romania
26. Slovakia
27. Slovenia
28. Spain
29. Turkey
30. United Kingdom
31. United States

It is worth noting that Bosnia and Herzegovina, Georgia, Sweden, and Ukraine are aspiring members of NATO.