The Berezina or Byarezina[2] (Belarusian: Бярэзіна, romanized: Biarezina,[3] IPA: [bʲaˈrɛzʲinɐ]; Russian: Березина) is a river in Belarus and a right tributary of the Dnieper.

The width of the river is 15–20 m, the maximum is 60 m. The banks are low (up to 0.5 m), steep in some areas (up to 1.5 m high), sandy, and the floodplain is swampy.

Its main tributaries are Bobr, Klyava, Ol'sa and Ala [be; ru] from the left and Hayna and Svislach from the right.

Peat bogs cover 430 km2 and thus occupy a large part of the reserve.

These open peat zones have remained virtually untouched and are among Europe's largest bogs.