The Danube

The Danube is Europe’s longest river, longest river's fastest too in places, regularly flowing at 10 or even 15 knots, a fact to which I can attest.

Russian river Volga

The longest river in Europe is Russian river Volga, the highest mountain of Europe – Elbrus.

The Volga : (RussianВо́лга)

The Volga (Russian: Во́лга) is the longest river in Europe.

Volga River, which has a length of 3,530 km,

Volga River, which has a length of 3,530 km, is the longest river in Europe.

the Rhine River

the Rhine River is Europe’s longest river, beginning as a glacial drip high in the Swiss Alps and flowing 870 miles northward to the North Sea.

the Volga, which flows southward into the Caspian Sea

The longest European river is the Volga, which flows southward into the Caspian Sea.