The Loire is the longest river in France, stretching for over 1000 kilometers from its source in the Massif Central to the Atlantic Ocean. It is the longest river entirely within France and is known for its many tributaries, including the Allier, Cher, Indre, Vienne, and Sarthe rivers. The Loire is also home to numerous castles, vineyards, and other historical sites, making it a popular tourist destination.