Samastipur constituency is one of the 243 legislative assembly constituencies of Bihar and is located in the district of the same name. The current MLA from this constituency is Akhtarul Islam Shahin of the Rashtriya Janata Dal (RJD) who secured 68,507 in the 2020 general elections, beating Ashwamedh Devi of Janata Dal (United) (JDU) by a margin of 4,714 votes.

In the 2020 general election the total number of electors registered in this constituency was 279,144. Out of this, the male electors amounted to 149,108, female electors amounted to 130,029 and 7 electors belonged to the third gender. Out of the total registered electors 166,269 electors cast their votes marking the voter turnout at 59.56 per cent.

The recent data from 2024 by the election commission shows that there are 276,876 total registered electors in Samatipur constituency; out of which 146,134 electors are male, 130,733 electors are female and 9 electors are of the third gender. Polling for this constituency took place in the first phase of elections on November 6, 2025.

Samastipur has a rich and vibrant cultural heritage with traditional dance forms like Kathghorwa nach and Jhijhia. This area was separated from the Darbhanga district in 1972. Rivers such as the Budhi Gandak, Kosi, and the Ganges flow through Samastipur. Samastipur is a major agriculture hub for cash crops which include rice, wheat, maize and tobacco as well as horticulture crops like litchis and mangoes. This constituency covers an approximate land area of 151.82 square kilometers. Samastiarpur constituency shares its borders with five other legislative assembly constituencies of Bihar which are Kalyanpur, Warisnagar, Ujaipur, Sarairanjan and Morwa.