| Old Brahmaputra River | |
| Pushpin Map: | Bangladesh |
| Pushpin Map Caption: | Location in Bangladesh |
| Subdivision Type1: | Country |
| Subdivision Name1: | Bangladesh |
| Subdivision Type2: | Division |
| Subdivision Name2: | Rangpur Division Mymensingh Division |
| Subdivision Type3: | District |
| Subdivision Name3: | Gaibandha, Jamalpur, Mymensingh, Sherpur |
| Source1: | Brahmaputra River |
| Mouth: | Meghna River |
| Mouth Coordinates: | 24.0333°N 90.9833°W |
The Old Brahmaputra River (Bengali: পুরাতন ব্রহ্মপুত্র নদী|Purātana Brahmaputra Nadī) is a distributary of the Brahmaputra River in north-central Bangladesh.[1] Historically it constituted the main stem of the Brahmaputra, however, the larger river's primary outflow was redirected via the Jamuna River after the 1762 Arakan earthquake.[2] Today, the Old Brahmaputra has been relegated to a minor river with much less flow than its former self. The river branches off from the Brahmaputra in Jamalpur District and flows southeasterly for approximately before meeting the Meghna River in Kishoreganj District.