Long Seniai
{{Infobox settlement
| name = Long Seniai
| image_skyline =
| image_caption =
| image_flag =
| image_shield =
| image_map =
| coordinates = {{coord|3.45|114.95|region:MY|display=inline,title}}
| pushpin_map = Borneo
| pushpin_label_position = right
| subdivision_type = Country
| subdivision_name = {{flag|Malaysia}}
| subdivision_type1 = State
| subdivision_name1 = {{flag|Sarawak}}
| 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 {{convert|553.7|km|mi|0}} east-north-east of the state capital Kuching.
Neighbouring settlements include:
- Long Merigong {{convert|11.3|km|mi|1}} east
- Long Tebangan {{convert|13.1|km|mi|1}} southwest
- Long Tap {{convert|18.3|km|mi|1}} southwest
- Long Akah {{convert|23.7|km|mi|1}} southwest
- Long Datih {{convert|24.1|km|mi|1}} east
- Long San {{convert|24.9|km|mi|1}} southwest
- Long Daloh {{convert|25.7|km|mi|1}} northwest
- Long Lellang {{convert|25.7|km|mi|1}} east
- Long Selatong {{convert|28.3|km|mi|1}} southwest
- Aro Kangan {{convert|28.5|km|mi|1}} east