The Karadarya River is the left branch of the Syrdarya River flowing on the territory of Kyrgyzstan and Uzbekistan.

Its length is 180 km, the catchment area is 30.1 ths km², and the mean flow rate is 120 m³/s.

It is formed by the confluence of the Karakudja and Tar rivers originating in the slopes of the Fergana and Alay ranges and flows westward. First, the Karadarya River flows through a wide valley in a multi-branching pebbled channel. Before escaping to the Fergana valley, the river breaks through the Kampyrravat gorge where it runs through a floodplain swamp here and there breaking up into several arms. Then it joins the Naryn River to form the Syrdarya.

The river is snow and glacier-fed. Its peak flow takes place in June, and the lowest flow in winter. The river’s major tributaries are: Kurshab on the left side; Yassy, Kugart, and Tentaksay (Karaunkur) on the right. The Karadarya River is very important for irrigation. The Andizhan reservoir built in the river supplies water for irrigation in the Fergana Valley. In this Valley, Karadarya is dammed by the Kuygan-Yar dike and runs across the Big Fergana Canal.

Large human settlements located along the river are Uzgen, Topolino, and Karabagish.