| Mairwa | |
| Settlement Type: | CD block |
| Pushpin Map: | India Bihar |
| Pushpin Label Position: | right |
| Pushpin Map Caption: | Location in Bihar, India |
| Coordinates: | 26.23°N 84.15°W |
| Subdivision Type: | Country |
| Subdivision Name: |  India |
| Subdivision Type1: | State |
| Subdivision Name1: | Bihar |
| Subdivision Type2: | District |
| Subdivision Name2: | Siwan |
| Subdivision Type3: | Subdivision |
| Subdivision Name3: | Siwan |
| Government Type: | Community development |
| Governing Body: | Mairwa block |
| Seat Type: | Headquarters |
| Seat: | Mairwa |
| Unit Pref: | Metric |
| Area Total Km2: | 69.17 |
| Elevation M: | 65 |
| Population Total: | 113499 |
| Population As Of: | 2011 |
| Population Density Km2: | auto |
| Demographics Type1: | Languages |
| Demographics1 Title1: | Official |
| Demographics1 Info1: | Bhojpuri, Hindi |
| Timezone1: | IST |
| Utc Offset1: | +5:30 |
| Postal Code: | 841239 |
| Blank1 Name Sec1: | Lok Sabha constituency |
| Blank1 Info Sec1: | Siwan |
| Blank2 Name Sec1: | Vidhan Sabha constituency |
| Blank2 Info Sec1: | Ziradei |
Mairwa community development block (CD block) or Mairwa block is a notified area (community development block) in Siwan district in the Indian state of Bihar. It is one of 13 blocks of Siwan subdivision.
The total area of the block is 69.17km2 and the total population of the block is 113,499.[1] Mairwa city is the headquarters of this block.
The block is divided into one nagar panchayat (urban) and many gram panchayats (rural).[2]
Some villages of Mairwa block in different panchayats are:
Mairwa, situated in the western part of Bihar, borders the Indian state of Uttar Pradesh. It was originally a block of Siwan district, approximately 20 km from Siwan which in ancient days formed a part of Kosala Kingdom. It is geographically situated at 25º35 North and 84º1 to 84º20 East. Mairwa is bounded on the east by the Siwan district headquarters, on the north by Gopalganj district and on the west and south by two districts of Uttar Pradesh: Deoria and Ballia.