| Longcanoe Lake | |
| Pushpin Map: | Ontario |
| Location: | Thunder Bay District, Ontario, Canada |
| Coords: | 48.9281°N -87.3658°W |
| Inflow: | Whitesand River from Gumboot Lake |
| Outflow: | Whitesand River to Hornblende Lake |
| Basin Countries: | Canada |
| Length: | 1.1km (00.7miles) |
| Width: | 0.25km (00.16miles) |
| Elevation: | 345m (1,132feet) |
Longcanoe Lake is a narrow lake in Thunder Bay District, Ontario, Canada about 15km (09miles) north-east of the community of Rossport and 11km (07miles) north of Highway 17. It is oriented in a north–south direction and is about 1100m (3,600feet) long and 250m (820feet) at its widest, at its north end. The lake is part of the Whitesand River system and flows out at its south end via this river into Hornblende Lake, and eventually via the Hewitson River into Lake Superior. A mine access road travels along the eastern shore of the lake.