Bolshoy Uzen River

Bolshoy Uzen ( _ru. Большой Узень) is a river in Saratov Oblast of Russia and West Kazakhstan Province of Kazakhstan. It is 650 km in length, with a drainage basin of 15 600 km².

The Bolshoy Uzen has its sources on the western edge of the Obshchy Syrt highlands of Russia, and flows in a generally southerly direction over the steppes of the Caspian Depression. It terminates in West-Kazakhstan, in a network of small lakes and swamps called the Kamysh-Samarskiye Lakes. The Bolshoy Uzen runs parallel to the Maly Uzen River, some 50 km further west.

Most of the river's waters comes from melting snow, and its discharge it therefore at its peak in April, while in the summer parts of the river will dry up completely. At Novouzensk the discharge varies from 7.3 m³/s to 393 m³/s. The river freezes over in December, and stays icebound to the end of March - beginning of April.

The town of Novouzensk is situated at the Bolshoy Uzen. The river is used for water supply and irrigation.