The answer to the question of the highest mountain in France is not necessarily as straightforward as you may think.

Mont Blanc, standing at 4810 metres above sea level, is not only the tallest mountain in Western Europe but as the highest summit of the Alps it is also the tallest mountain to stand on French soil. However, the mountain is shared with neighbouring country; Italy. Incidentally the mountain is called Monte Bianco by the Italians.

The true summit of Mont Blanc has swapped hands over the centuries. For a long time it was "owned" by the Duchy of Savoy, before the French Revolution intervened. Finally, with the Italian war of unification, in 1860, a treaty was signed by Vittorio Emanuele of Savoy and Napoleon the III of France which essentially carved up Savoy. One year later, on the 7th of March 1861 an agreement was signed by both sides detailing for the very first time that Mont Blanc / Monte Bianco is located on the border of France and Italy.

Maps of the period show the summit as lying partly in France and partly in Italy. Since then Mont Blanc can be considered the highest mountain in France.

Highest Peak only in France.

However if you are looking for the highest peak to be solely in France you would have to downscale slightly. There a few candidates for the tallest mountain solely on French soil which we list below:

Dôme de Goûter - 4304 m

The Dôme de Goûter is in effect a sort of flat hunch or shoulder below Mont Blanc and is considered an Alpine peak in its own right.

Mont Blanc du Tacul - 4248 m

Mont Blanc du Tacul is also part of the Mont Blanc massif. This granite summit rises between the Aiguille du Midi and Mont Blanc itself.

Aiguille Verte - 4122 m

The Aiguille Verte also stands, a rocky pyramid, in the Mont Blanc Massif

Barre des Ecrins - 4102 m

Outside of the Mont Blanc Group the highest mountain in France is the Barre des Ecrins. It was indeed for a long time genuinely the highest as Savoy was part of the Kingdom of Sardinia. Now it is completely within French territory in the Provence-Alpes-Côte region.