Jainagar (also spelled as Jaynagar) is a town and a notified area of Madhubani district in the Indian state of Bihar.

As of the 2011 India census, Jainagar had a total population of 21,782.

[1] Jaynagar is a border town in the Madhubani district of the Mithila region in Bihar, India.

The Jaynagar Railway Station of the town is one of the major terminals in the Samastipur division of the East Central Indian Railway Zone.

[2] Shilanath Mahadev Mandir at the outskirts of the town is an important place for the Hindu pilgrimage in the region.