The French Constitution declares that French is the only language of France. Although France has declared some regional languages to be language of France, France is prevented from ratifying the EU Treaty on Minority Languages due to its Constitution.
A UNESCO report on endangered languages shows that French is seriously threatening 26 languages or dialects in France, including: Basque, Burgundian, Breton, Champenois, Corsican, Flemish, Franche-Comté, Moselle Franconian, Rhine Franconian, Francoprovençal (Arpitan), Gallo, Ligurian, Lorrain, Norman, Occitan (Auvergne, Gascony, Languedoc, Limousin, Provençal), Picard and Poitevin-Saintonge.
Of these, the following are langues d’oil, related to French: Picard, Gallo, Burgundian, Champenois, Franche-Comté, Lorrain, Norman,and Poitevin-Saintonge. These are actually separate languages or patois. They are not dialects of French. Many of them split from langue d’oil long ago. In general, they are quite incomprehensible to French speakers. Let’s look at them:
Burgundian is spoken in Burgundy around Dijon. It is not in good shape, but it still has a lot of speakers. Not intelligible with Standard French. It has about 2,000 native speakers.
Champenois is spoken in Champagne around Reims and in neighboring Belgium, where it is a regionally protected language. I don’t have much information on it, but it’s probably not in good shape. Not intelligible with Standard French.
Franche-Comté is still spoken in Franche-Comte around Besancon. It still has some elderly speakers, but it’s probably not in good shape. Not intelligible with Standard French. It has 3,700 speakers in Switzerland. Figures for France are not known.
Gallo is spoken in eastern Brittany around Rennes. It is still in reasonably good shape. Not intelligible with Standard French. 28,000 speakers. 200-400,000 with at least passive knowledge.
Lorrain is spoken in the northwest of France in the Lorrain region around the city of Nancy, the Vosges Mountains and even into Belgium. Not intelligible with Standard French.
Norman is spoken on the coat of Normandy around Le Havre and on the Channel Islands. This is actually several separate languages. It is not doing well, and is doing especially poorly on the Islands where the influence of English is very strong. Not intelligible with Standard French. Up to 243,000 speakers.
Picard has about 700,000 speakers in far northwest France around Calais, Lille and Dunkirk and in Belgium. It is probably actually two separate languages. Not intelligible with Standard French.
Poitevin-Saintongeais is spoken on the west-central coast of France and around Poitiers. Eleanor of Acquitaine was actually a Poitevin speaker. This is actually two separate languages. Saintongeais is still widely spoken. Poitevin is doing well and has 150-500,000 speakers.
There are actually other langues d’oil, but I won’t list them.
Basque is spoken by only about 10% of the population of the French Basque country. This area is a huge tourist destination, and that has really hurt the Basque language badly in France. Basque is in much better shape in Spain. French Basques are rather quiet and not particularly militant, but there was an armed group at one point. Mostly the French Basque country is used by ETA radicals from Spain as a hideout from the law.
Breton is the Gaelic language related to Welsh that is spoken in Brittany on the northwest edge of France. This language does have 200,000 speakers, but most of them are over age 50. There are also 500 schools or diwans teaching the language. Although this sounds promising and Breton is in better shape than the other languages listed here, there are a lot of worries about this language. For one thing, the French won’t allow it to be taught in French schools.
Corse is spoken on the island of Corsica by about 40% of the population. It is not in good shape. There is a large independence movement in Corsica with huge support. Corse is really just an ancient Tuscan Italian dialect from about ~1500. Speakers of Standard Italian, based on Florentine Tuscan, can understand Corse easily. 100,000 speakers, 1/3 of the island, but many of them are older. Some young people are learning it, but it starts too late – by high school. Instruction needs to start earlier.
Flemish is still spoken by about 20,000 speakers in the far northwest of France around Dunkirk. It is not in good shape at all.
Francoprovençal or Arpitan is an old language with 112,000 speakers that split away from the langue d’oil at about the time it was first becoming consolidated around 800-900. Arpitan split from Catalan-Occitan around 600. This language is also spoken in Italy and Switzerland. It is probably actually 10 or more languages, since there is poor communication among the dialects. It is spoken in the part of France near Switzerland, in the Savoy and around Lyon, Grenoble and St. Etienne to the west of Switzerland.
This language is doing very poorly in France but was still very widely spoken until the 1970’s and 1980’s. It probably resembles French more than any other language.
Ligurian is a Gallo-Romance language similar to a cross between French and Italian. It is mostly spoken around Genoa in Italy, but it is spoken in several dialects along the coast of southeastern France near the border with Italy in the Maritime Alps. Up to 2 million speakers total, but the language is still thought to be in poor shape because few young people are learning it.
Moselle Franconian is spoken in an area of the Alsace-Lorraine on the border with Germany. The variety spoken in France is called Lorraine Franconian and is not in good shape. This German language is not intelligible with Standard German. 78,000 speakers.
Occitan (Auvergnat, Gascon, Nissart, Mentonasque, Monegasque, Languedoc, Limousin, Cisalpine, Provençal dialects) is spoken in the south of France by up to 7 million people understand the language, and 1 million speak it as a first language. It is probably doing better than most of the languages listed in here, but it does not have a secure position.
This is the ancient language of the Troubadours and it is closely related to Catalan, having split from Catalan around 1000. Catalan-Occitan started to split away as a separate language around 800. Occitan itself split from langue d’oil in the 800’s. From 1000-1600, Catalan and Occitan evolved along similar lines.
It is quite unintelligible to French speakers. Sort of a cross between French and Spanish. The question of whether or not the dialects can understand each other and to what degree is a thorny one that does not have good answers. Nissart, Gascon, Limousin, Cisalpine and Languedocien are definitely separate languages.
Rhine Franconian is spoken in France in the same general region as Moselle Franconian, except a bit to the west. It is intelligible with Standard German or with Moselle Franconian. It is not doing very well.