How many countries are there whose mother tongue is Spanish?

It's tricky to say definitively how many countries have Spanish as their "mother tongue" because:

* Official vs. Native: Some countries have Spanish as their official language, but it's not the primary language spoken by the majority of the population.

* Regional Variations: Within a country, there can be different languages spoken depending on the region.

* Immigrant Populations: Many countries have large Spanish-speaking immigrant communities.

That being said, these 20 countries have Spanish as their official language and are generally considered to have Spanish as a dominant language:

1. Argentina

2. Bolivia

3. Chile

4. Colombia

5. Costa Rica

6. Cuba

7. Dominican Republic

8. Ecuador

9. El Salvador

10. Equatorial Guinea

11. Guatemala

12. Honduras

13. Mexico

14. Nicaragua

15. Panama

16. Paraguay

17. Peru

18. Spain

19. Uruguay

20. Venezuela

It's important to remember that this list focuses on official languages and general language dominance. The actual number of countries where Spanish is the primary language spoken by the majority of the population might be slightly different.