Bulgaria may be a relatively small country, but it has an extensive network of rivers flowing from its mountains toward the Danube, Black Sea, and Aegean Sea. There are hundreds of rivers across Bulgaria, ranging from short mountain streams to major waterways that cross international borders.

The longest rivers in Bulgaria can be ranked in different ways. The Danube is by far the longest river associated with the country, forming much of Bulgaria’s northern border with Romania, while the Maritsa and Struma continue beyond Bulgaria into neighboring countries. The Iskar River, at 368 km, is the longest river that flows entirely within Bulgaria.