Bathnaha (Vidhan Sabha constituency) (Hindi: बथनाहा विधान सभा निर्वाचन क्षेत्र) is an assembly constituency in Sitamarhi district in the Indian state of Bihar. It is reserved for scheduled castes. It was an open seat earlier.
As per Delimitation of Parliamentary and Assembly constituencies Order, 2008, 24. Bathnaha (Vidhan Sabha constituency) (SC) is composed of the following: Bathnaha and Majorganj community development blocks; Bagha, Khap Khopraha, Marpa, Kanhauli, Kachor, Bhutahi, Madhesra, Ghurghura, Hanuman Nagar and Bishanpur Gonahi gram panchayats of Sonbarsha CD Block.
Bathnaha (Vidhan Sabha constituency) is part of 5. Sitamarhi (Lok Sabha constituency).
Election results 
In the November 2010 state assembly elections, Dinkar Ram of BJP won the 24 Bathnaha assembly seat defeating his nearest rival Lalita Devi of LJP. Contests in most years were multi cornered but only winners and runners are being mentioned. Nagina Devi of LJP defeated Surydeo Rai of RJD in October 2005 and February 2005. Suryadeo Rai of RJD defeated Raj Kishore Singh Kushwaha of SAP in 2000. Suryadeo Rai representing JD defeated Indal Singh Navin of SAP in 1995 and Rajendra Singh, Independent, in 1990. Ram Niwas of Congress defeated Suryadeo Rai representing Congress (S) in 1985. Suryadeo Rai representing Congress (U) defeated Capatain Ram Niwas of Congress in 1980. Suryadeo Rai of Congress defeated Laliteswar Prasad Singh of JP in 1977.