| Seki River | |
| Name Other: | 関川 |
| Subdivision Type1: | Country |
| Subdivision Name1: | Japan |
| Subdivision Type2: | State |
| Subdivision Name2: | Honshu |
| Subdivision Type3: | Region |
| Subdivision Name3: | Niigata Prefecture, Nagano Prefecture |
| Length: | 64km (40miles) |
| Source1: | Niigata-Yakeyama |
| Source1 Elevation: | 2400m (7,900feet) |
| Mouth: | Sea of Japan |
| Basin Size: | 1140km2 |
The Seki River (関川) is a Class A river in Niigata Prefecture and Nagano Prefecture, Japan.[1] [2] Approximately 210,000 people live in the basin area.