Jamalpur, city, central Bihar state, northeastern India. It is situated just south of Munger near the Ganges (Ganga) River.
Jamalpur was established in 1862 as a railway settlement and contains large locomotive engineering workshops as well as major iron and steel foundries. Slate quarries are located to the southwest. The city has colleges affiliated with Tilka Manjhi Bhagalpur University. It was constituted a municipality in 1883. Pop. (2001) 96,983; (2011) 105,434.