Which of these is the longest river to flow only within the borders of France?

The Loire is the longest river which flows within the boundaries of France. It has a length of 1,012 kilometres (629 mi) and it drains an area of 117,054 km2 (45,195 sq mi), or more than a fifth of France's land area.

It rises in the southeastern quarter of the French Massif Central in the Cévennes range which is in the department of Ardèche at 1,350 m (4,430 ft) near Mont Gerbier de Jonc. It flows north through Nevers to Orléans, then west through Tours and Nantes until it reaches the Bay of Biscay (Atlantic Ocean) at Saint-Nazaire.

Its main tributaries include the rivers Nièvre, Maine and the Erdre on its right bank, and the rivers Allier, Cher, Indre, Vienne, and the Sèvre Nantaise on the left bank.

The Loire gives its name to six departments namely Loire, Haute-Loire, Loire-Atlantique, Indre-et-Loire, Maine-et-Loire, and Saône-et-Loire. The central part of the Loire Valley, located in the Pays de la Loire and Centre-Val de Loire regions, was added to the World Heritage Sites list of UNESCO on December 2, 2000. Vineyards and châteaux are found along the banks of the river throughout this section and are a major tourist attraction.

The River Marne is 319 miles (513 km), the River Seine is 482 miles (776 km), and the River Dordogne is 300 miles (483 km) and all flow within the confines of France.The longest river that runs partially through France is the Rhine which is 764 miles (1230 km) which is shared with 5 other countries.