1. France (obvious, but important!)
2. Canada (Quebec and other regions)
3. Belgium (alongside Dutch and German)
4. Switzerland (alongside German, Italian, and Romansh)
5. Luxembourg (alongside German)
6. Monaco
7. Haiti
8. Senegal
9. Côte d'Ivoire
10. Cameroon
There are many other countries where French is spoken, but these are the top 10 where it is an official language.