Is the Volga Europe's Longest River?

Yes. The Volga River stretches ~3,700 km (2,300 mi) from the Valdai Hills to the Caspian Sea, entirely within Russia. It drains 40% of European Russia, passes major cities (Tver, Yaroslavl, Nizhny Novgorod, Kazan, Samara, Saratov, Volgograd), and carries half of Russia's river freight. The Danube (2,850 km) is Europe's second-longest.