| Jainagar | |
| Other Name: | Jaynagar |
| Settlement Type: | Town |
| Pushpin Map: | India Bihar |
| Pushpin Map Caption: | Location in Bihar |
| Coordinates: | 26.5925°N 86.1372°W |
| Subdivision Type: | Country |
| Subdivision Name: | India |
| Subdivision Type1: | State |
| Subdivision Name1: | Bihar |
| Subdivision Type2: | District |
| Subdivision Name2: | Madhubani |
| Unit Pref: | Metric |
| Population Total: | 21,7820 |
| Population As Of: | 2017 |
| Population Density Km2: | auto |
| Demographics Type1: | Languages |
| Demographics1 Title1: | Official |
| Demographics1 Info1: | Maithili, Hindi |
| Timezone1: | IST |
| Utc Offset1: | +5:30 |
| Postal Code Type: | PIN |
| Postal Code: | 847226 |
| Area Code: | 06246 |
| Area Code Type: | Telephone code |
| Blank1 Name Sec1: | Lok Sabha constituency |
| Blank1 Info Sec1: | Jhanjharpur |
| Blank2 Name Sec1: | Vidhan Sabha constituency |
| Blank2 Info Sec1: | Khajauli |
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. Males constituted 51% of the population and females 49%. Jainagar had an average literacy rate of 79%, higher than the national average of 74.04%. Male literacy was 86%, and female literacy was 71%. 16% of the population were under 60 years of age.[1]