Here's a list:
Africa:
* Benin
* Burkina Faso
* Burundi
* Cameroon
* Central African Republic
* Chad
* Comoros
* Congo, Democratic Republic of the
* Congo, Republic of the
* Côte d'Ivoire
* Djibouti
* Gabon
* Guinea
* Madagascar
* Mali
* Mauritania
* Niger
* Rwanda
* Senegal
* Seychelles
* Togo
Americas:
* Canada
* Haiti
Europe:
* Belgium
* France
* Luxembourg
* Monaco
* Switzerland
Oceania:
* Vanuatu
Note: While French is an official language in many countries, it might not be the most widely spoken language in some of them. For example, English is more widely spoken in Canada than French.