Africa:
* Central African Republic: French is the official language and widely spoken.
* Chad: French is the official language and widely spoken.
* Cameroon: French is one of the official languages and widely spoken.
* Democratic Republic of Congo: French is one of the official languages and widely spoken, particularly in urban areas.
* Republic of Congo: French is the official language and widely spoken.
* Côte d'Ivoire: French is the official language and widely spoken.
* Gabon: French is the official language and widely spoken.
* Guinea: French is the official language and widely spoken.
* Mali: French is the official language and widely spoken.
* Niger: French is the official language and widely spoken.
* Senegal: French is the official language and widely spoken.
* Togo: French is the official language and widely spoken.
Other:
* Belgium: French is one of the official languages, alongside Dutch and German.
* Canada: French is one of the official languages, alongside English.
* Switzerland: French is one of the official languages, alongside German, Italian, and Romansh.
* Luxembourg: French is one of the official languages, alongside Luxembourgish and German.
* Monaco: French is the official language and widely spoken.
* Vietnam: French is spoken by a significant minority, particularly in the older generation.
Important Notes:
* The prevalence of French as a second language varies within each country. It's more common in urban areas and among educated populations.
* Many other countries have significant French-speaking communities, often due to immigration from France or its former colonies.
* This is not an exhaustive list, and other countries could be included depending on the definition of "common" and "second language".
It's crucial to understand that language use is complex and dynamic, and generalisations can be misleading.