This article lists the principal rivers of Europe with their main tributaries.

This section does not cite any sources. (October 2021)

The border of Europe and Asia is here defined as from the Kara Sea, along the Ural Mountains and Ural River to the Caspian Sea. While the crest of the Caucasus Mountains is the geographical border with Asia in the south, Georgia, and to a lesser extent Armenia and Azerbaijan, are politically and culturally often associated with Europe; rivers in these countries are therefore included.

The list is at the outset limited to those rivers that are at least 250 km long from the most distant source, have a drainage basin (catchment area, watershed) of at least 10,000 km² (3,900 sq mi), or have a mean discharge (volume, flow) of at least 150 m³/s (5,300 cu ft/s). Also included are a number of rivers (currently 47) that do not meet these criteria, but are very well known and/or nearly make the mark. Examples of these are the Arno, Ruhr, Saar, and Clyde. See the lists of rivers for individual countries linked to at the bottom of the page for smaller rivers.

The rivers are ordered from those flowing to the extreme northeast into the Arctic Ocean, following the coastline anticlockwise all the way to the southeastern coast of the Black Sea. Iceland and the British Islands are included via virtual connections with northern Norway and across the Strait of Dover and the North Channel, respectively. Finally, rivers draining into the Caspian Sea are listed from Azerbaijan to the Ural River.

The table can be sorted by each column. The first three columns give a ranking for (maximum) length, area and volume of those rivers flowing into the sea or an endorheic lake down to the cut-off values. No ranking of tributaries is attempted, as the concept is too contentious; for example, hydrologically the middle and upper Volga could be considered a tributary of the Kama, in which case it would be the fifth or sixth longest river in Europe. Instead it does not appear in the table at all.

The commercial and geopolitical importance of rivers is not ranked here. As a transportation artery, a river may unite a region commercially and economically, but major rivers, as barriers to travel, may also form political boundaries between states. The Danube, the second longest river in Europe, is notable for flowing through or past ten countries; the Rhine through or past six. The Volga, the longest river in Europe, unites a huge region of European Russia; eleven of the twenty largest cities in Russia lie on its banks. The Loire and the Po unite important regions within France and Italy respectively. The most important rivers in Europe include Rhone, Elbe, Oder, Tagus, Thames, Don and Dnieper, among others.^{[further explanation needed]}

The measurements shown are drawn from sources deemed most reliable, but still are often uncertain, especially when other sources disagree wildly. For example, the Siret in Romania and Ukraine is 726 km long with a basin of 44,000 km² according to the Great Soviet Encyclopedia, 647 km (44,811 km²) according to a Romanian management plan for the Siret basin ^[1] and 559 km (47,610 km²) according to the extensive transboundary rivers study by the Economic Commission for Europe.^[2]

Length estimates for rivers depend on a number of variables:

• The estimate will be larger when the curves of the river are traced at a smaller scale.
• The choice of the source obviously has an impact. Here we attempt to list the most distant source. When that involves a tributary nearer the mouth of the river, the length of the nominal river is listed as well, if it meets the above criteria.
• Rivers flowing into estuaries have an arbitrary lower end. The channel of such a river through an estuary is usually included in the length when it is exposed at low tide.
• The length of a watercourse through a reservoir or lake is open to interpretation. For this table, when a source for the total length of a river system involving lakes is lacking, the shortest possible course through the lakes is used
• Over time, a river's length can change through canalization, the creation of reservoirs, and natural changes in the water course.

The catchment areas are more consistent between sources. However, in low relief the watershed is less obvious, while underground connections (especially in karst systems) further complicate area measurements. Unless excellent sources are available, the areas below 70°N latitude are taken from the HydroBASINS project.^[3] The River Networks and Ramsar Sites Information Service websites provide convenient interfaces to assess the accuracy of many of the basins. Areas for rivers above 70°N are warned^{[clarification needed]} and found to be less reliable.

The listed multiyear mean discharges are even less reliable than the lengths. Underestimates are most common, as the gauging stations are often far above the mouth, so that only a fraction of the drainage basin is represented. On the other hand, the highest volume of a river may not be at the mouth due to water loss by human usage, diversion (e.g. through distributaries), evaporation, or underground drainage.