The Medveditsa or Medveditza (/mɛdˈvɛdɪtsə/; Russian: Медведица, romanized: Medvedica, IPA: [mʲɪdˈvʲedʲɪtsə]) is a river in Volgograd and Saratov Oblasts in Russia, a left tributary of the Don. The name means she-bear, and according to legend, it alludes to the large population of bears in the area in earlier times. It is 745 kilometres (463 mi) long, with a drainage basin of 34,700 square kilometres (13,400 sq mi).

The river has its sources on the Volga Uplands, in the northeastern parts of Saratov Oblast, and flows mainly in a southwestern direction. It joins the Reka Don in Volgograd Oblast near Zatonski. Its largest tributaries are, from the right: Balanda and Tersa, and from the left: Idolga, Karamysh and Archeda.

The towns of Petrovsk, Atkarsk, Medveditsa, Zhirnovsk, and Mikhaylovka are situated on the Medveditsa. The river is navigable to Atkarsk.

A variety of fish is found in the Medveditsa River: catfish, pike, bream, asp, perch, chub, perch, tench, roach, gudgeon and others. In the late 80s there were a lot of sterlet.

Forests along both banks of the river have a wide variety of birds, medicinal herbs, wild berries, fruits and flowers.