| Long Seniai | |
| Coordinates: | 3.45°N 114.95°W |
| Pushpin Map: | Borneo |
| Pushpin Label Position: | right |
| Subdivision Type: | Country |
| Subdivision Name: |  Malaysia |
| Subdivision Type1: | State |
| Subdivision Type2: | Administrative Division |
| Subdivision Name2: | Marudi |
| Elevation M: | 566 |
Long Seniai (also known as Long Sinei) is a longhouse settlement in the Marudi division of Sarawak, Malaysia. It lies approximately 553.7km (344.1miles) east-north-east of the state capital Kuching.
Neighbouring settlements include: