This is a list of tributaries of the Danube by order of entrance.
The Danube is Europe's second-longest river, with a length of 2,850 kilometres (1,770 mi), and a drainage basin of 801,463 square kilometres (309,447 sq mi). It starts in the Black Forest in Germany as two smaller rivers—the Brigach and the Breg—which join at Donaueschingen, after which it is known as the Danube.
The Sava is a river in Central and Southeast Europe, a right-bank and the longest tributary of the Danube. From its source in Slovenia it flows through Croatia and along its border with Bosnia and Herzegovina, and finally reaches Serbia, feeding into the Danube in its capital, Belgrade.
The Sava is 990 kilometres (615 miles) long, including the 45-kilometre (28 mi) Sava Dolinka headwater rising in Zelenci, Slovenia. It is the largest tributary of the Danube by volume of water, and the second-largest after the Tisza in terms of catchment area (97713km²) and length. It drains a significant portion of the Dinaric Alps region, through the major tributaries of Drina, Bosna, Kupa, Una, Vrbas, Lonja, Kolubara, Bosut and Krka. The Sava is one of the longest rivers in Europe and among the longest tributaries of another river.