river in northeastern India, rising with its many tributaries, notably the Bokaro and Konar, in the Chota Nagpur plateau of south-central Bihar state. It follows a generally eastward course for 368 miles (592 km) through West Bengal to join the Hugli (Hooghly) River (Hugli River) southwest of Kolkata (Calcutta) (Calcutta).

The Damodar valley along the Bihar–West Bengal border includes India's most important coal- and mica-mining fields and has long been an area of active industrial development. The major coalfields (Jharia, Raniganj, and Giridih) are mostly open-pit and are easily mined. The Damodar Valley Corporation, which began work in 1948, constructed four multipurpose dams to form a series of reservoirs—Tilaiya, Maithon, Konar, and Panchet Hill. Also included is the Durgapur diversionary barrage (dam) and an 80-mile (130-km) navigation canal linking the coalfields with the Hugli-Kolkata industrial complex. The project provides for flood control, hydroelectricity, coal-fired thermal power plants, irrigation of about 950,000 acres (385,000 hectares) chiefly in West Bengal, afforestation, fish breeding, recreation, and the general development of agriculture and industry throughout the valley, which experienced a great influx of people during the 20th century. Numerous towns, including Dhanbad, Jharia, and Sindri, are connected by a dense rail and road network.