100 Longest Rivers in Europe - with a Map

River: A body of water which has, according to the abovementioned source, no connection (arrow) to another.

River system: A system which consists of at least two rivers. There are, however, requirements for this:

A river system has been assumed if it has

1. its source in a lake which is fed by a river of another name (e.g. Göta River -> Lake Vänern -> Klar River)

2. its source at the confluence of two rivers, then following the longer one (e.g. Weser -> Werra)

3. headwaters bearing the same name (e.g. Sava Dolinka -> Sava)

This in return means, that a longer tributary joining the main river later somewhere along its way is NOT considered a river system (e.g. Volga -> Oka or Havel -> Spree)

An exception has been made for the Western Bug, which joins the Narew shortly before flowing into the Vistula. It would’ve otherwise been isolated from the remaining rivers.

Estuaries are included in river length (Elbe, Garonne, Southern Bug).