Here's a list of the top 25 most intelligent nations based on various metrics such as literacy rates, education levels, scientific research output, and other indicators.

1. Finland: Consistently ranked high in PISA (Programme for International Student Assessment) scores, Finland excels in literacy, math, and science.

2. South Korea: Known for its rigorous education system, South Korea consistently ranks high in PISA scores and has a high literacy rate.

3. Canada: Canada has a strong education system, high literacy rates, and a high level of scientific research output.

4. Netherlands: The Netherlands has a highly educated population, with a strong focus on science, technology, engineering, arts, and mathematics (STEAM) fields.

5. Switzerland: Switzerland is renowned for its excellent education system, high literacy rates, and strong scientific research output.

6. Denmark: Denmark has a high level of education attainment, low poverty rates, and a strong focus on innovation and entrepreneurship.

7. Singapore: Singapore is known for its highly competitive education system, with a strong focus on STEAM fields and a high literacy rate.

8. New Zealand: New Zealand has a well-regarded education system, high literacy rates, and a strong focus on environmental sustainability.

9. Australia: Australia has a highly educated population, with a strong focus on STEAM fields and a high level of scientific research output.

10. Japan: Japan is known for its highly competitive education system, with a strong focus on science and technology.

11. Sweden: Sweden has a highly educated population, with a strong focus on innovation and entrepreneurship.

12. Germany: Germany has a well-regarded education system, with a strong focus on STEAM fields and a high level of industrial productivity.

13. United Kingdom: The UK has a highly educated population, with a strong focus on research and development in fields like medicine and technology.

14. France: France has a well-regarded education system, with a strong focus on culture, art, and science.

15. Israel: Israel is known for its highly educated population, with a strong focus on STEAM fields and innovation.

16. United States: The US has a highly educated population, with a strong focus on research and development in various fields.

17. Norway: Norway has a highly educated population, with a strong focus on sustainability and environmental protection.

18. Austria: Austria has a well-regarded education system, with a strong focus on science and culture.

19. Belgium: Belgium has a highly educated population, with a strong focus on science, technology, engineering, and mathematics (STEAM) fields.

20. Iceland: Iceland has a highly educated population, with a strong focus on innovation and sustainability.

21. Ireland: Ireland has a highly educated population, with a strong focus on technology and entrepreneurship.

22. Spain: Spain has made significant improvements in education in recent years, with a growing emphasis on innovation and entrepreneurship.

23. Czechia: Czechia has a well-regarded education system, with a strong focus on science and technology.

24. Portugal: Portugal has made significant improvements in education in recent years, with a growing emphasis on innovation and entrepreneurship.

25. Estonia: Estonia has made significant strides in digitalization and e-government, with a highly educated population and strong STEAM education system.

Please note that this ranking is subjective and may vary depending on the criteria used to measure intelligence. Additionally, there are many other nations that excel in specific areas or have made significant progress in their education systems.

Sources:

* Programme for International Student Assessment (PISA) - https://www.oecd.org/pisa/

* Central Intelligence Agency (CIA) World Factbook - https://www.cia.gov/library/publications/the-world-factbook/index.html

* Various academic studies and research papers