Madhubani is one of the 40 Lok Sabha (parliamentary) constituencies in Bihar state in eastern India.

Jainagar Lok Sabha constituency included western assembly segments of Madhubani district besides Jale assembly segment from Darbhanga district.

After inclusion of Madhubani assembly segment, Jainagar Lok Sabha constituency was renamed as Madhubani and Ladania CD block and adjoining areas were taken out of it to be merged into newly formed Jhanjharpur Lok Sabha constituency in order to compensate for the loss of Madhubani assembly segment.

After this reorganisation, communist vote bank in the district was bifurcated and CPI had to face greater difficulties in winning the eastern Lok Sabha constituency of this district which was won by CPI candidate Bhogendra Jha in 1967 and 1971.

Before reorganisation in 1976, the following members were elected to Madhubani seat which comprised eastern part of Madhubani district including the district headquarters: After reorganisation in 1976, the following members were elected to Madhubani seat, which comprised western part of Madhubani district formerly known as Jainagar Lok Sabha constituency (the eastern constituency of the district renamed as Jhanjharpur in 1976): [5][6][7][8][9][10][11][12][13][14]