The rivers rise mainly in the highest mountains and flow into the Black Sea and into the Aegean Sea. Bulgaria has 526 rivers longer than 2.3 km. The only navigable river is the Danube, which lies along the North Bulgarian border. There are good prerequisites for the development of adventure tourism: wild waters – rafting and canoe, diving, hanggliding and paragliding in the river valleys of Vatcha, Iskar, Chepelarska, Struma, and Mesta rivers.

The longest rivers on the territory of Bulgaria (in km): Iskar (368.0 km), Toundga (349.5 km), Maritsa (321.6 km), Osum (341.0 km), Struma (290.0 km), Yantra (285.5 km), Kamchiya (244.5 km), Arda (241.3 km), Louda Kamchiya (200.9 km) and Roussenski Lom (196.9 km).

There are about 330 natural lakes; the largest are the Black Sea lakes (Alepou, Arkoutino, Pomorie, Beloslav, Bourgas, Varna and the Shabla lakes), the most numerous (over 260) are the high-mountain glacial lakes in the Rila and Pirin mountain ranges. Dams have been built as a part of waterpower systems – Iskar, Arda, Batak Water Power System, Belmeken-Sestrimo, Dospat-Vucha, and a great number of smaller dams.