Samastipur is one of the 40 Lok Sabha (parliamentary) constituencies in Bihar state in eastern India. It is reserved for Scheduled Castes. In the Legislative Assembly segment of this Lok Sabha constituency, Kushwaha, and Yadav caste are dominant, however, due to preponderance of other caste groups, Extremely Backward Castes and Schedule Castes also determine the election results.

Samastipur Lok Sabha constituency comprises the following six Vidhan Sabha (legislative assembly) segments:

^ by-poll

25°54′N 85°48′E / 25.9°N 85.8°E / 25.9; 85.8