This question has divided the French for decades.
Imagine a situation almost as divisive as the Dreyfus affair: family dinners that end in arguments, couples who break up and childhood friends who no longer speak to each other.
Do we say LA DOMBES or LES DOMBES?
Supporters of the plural form (Les Dombes) rely on three arguments: the “s” at the end of the “Dombes”, which is generally an indicator of the plural, the name of the town of Villars-les-Dombes, and the name of several establishments that bear the name “des Dombes” (also a plural form, as in “Le Fumet des Dombes”). Advocates of the singular form also point to the names of towns, like Saint-Marcel-en-Dombes (singular), the names of other regions that mostly takek the singular, like Bresse or Bugey, and finally the fact that the French administration designates this region in the singular.
The administration often has the last word!
So yes, we say LA Dombes.
Why Villars-LES-Dombes?
If we say La Dombes, then why do we say Villars-Les-Dombes?
The “les” in Villars-les-Dombes is not a plural article but a preposition meaning “near“.
Generally it is written “lès” (with an accent). It’s because of this confusion that many people use the plural form “Les Dombes” and many restaurants and businesses are called “x des Dombes”.
The “lès” is found in the names of several towns and villages, such as Saint Denis lès Bourg (meaning “Saint Denis near Bourg”).