Buxar is one of the key constituencies in the Bihar state assembly, this constituency is located in the Buxar district of the state. Buxar is also one of the 40 Lok Sabha constituencies from Bihar The current MLA from this constituency is Sanjay Kumar Tiwari alias Munna Tiwari of the Indian National Congress (INC) who secured 59,417 votes in the 2020 elections beating Parshuram Chaubey of the Bharatiya Janata Party (BJP) by a margin of 3,892 votes.
According to 2024 Elections Commission data, the total number of registered electors from this constituency is 298,589. 156,311 registered electors are male, 142,273 registered electors are female and 5 registered electors are of the third gender. The data from the last elections in 2020 show the total number of registered electors at 289,997 where 154,389 electors were male, 135,602 electors were female and 6 electors were of the third gender. In the 2015 elections, the data marked the total number of registered electors at 277,847 with 148,593 male electors, 129,248 female electors and 6 electors of the third gender were registered. In the 2020 elections, 164,530 out of the 289,997 total registered electors casted their votes, marking the voter turnout at 56.74% while in the 2015 elections 160,765 out of the 277,847 electors took part in polling, marking the voter turnout in 2015 at 57.86%. Polling for this constituency in the upcoming elections will be taken out in the first phase of elections on 6th November 2025. 
Buxar constituency covers an land approximate area of 230.77 square kilometers and the geographic coordinates of Buxar are 25° 38 '11.0"N 84° 06' 59.8"E. Three other Assembly constituencies in the state of Bihar share borders with Buxar constituency, which are: Brahampur, Dumraon and Rajpur. This constituency also shares an inter-state border with Uttar Pradesh.