| Rapid River | |
| Subdivision Type1: | Country |
| Subdivision Name1: | Canada |
| Subdivision Type2: | Province |
| Subdivision Name2: | Ontario |
| Subdivision Type4: | District |
| Subdivision Name4: | Algoma |
| Length: | 15km (09miles) |
| Source1: | Seymour Lake |
| Source1 Coordinates: | 46.7575°N -83.2322°W |
| Source1 Elevation: | 410m (1,350feet) |
| Mouth: | Mississagi River |
| Mouth Coordinates: | 46.7436°N -83.3981°W |
| Mouth Elevation: | 314m (1,030feet) |
| Tributaries Right: | Little Rapid River |
The Rapid River is a river in Algoma District, Ontario, Canada. The river is about 15km (09miles) long and begins at Seymour Lake at an elevation of 410m (1,350feet). It travels west and takes in its left tributary the Little Rapid River at an elevation of 408m (1,339feet). The river continues west over a small rapids and a waterfall before emptying into the Mississagi River at an elevation of 314m (1,030feet). A road, which begins at Highway 129 north of the river's mouth, parallels the majority of the river to Seymour Lake.