| Demijohn Lake | |
| Location: | Thunder Bay District, Ontario |
| Coords: | 48.9581°N -87.3717°W |
| Pushpin Map: | Ontario |
| Inflow: | Whitesand River |
| Outflow: | Whitesand River |
| Basin Countries: | Canada |
| Length: | 0.75km (00.47miles) |
| Width: | 0.1km (00.1miles) |
| Elevation: | 390m (1,280feet) |
Demijohn Lake is a J-shaped lake in Thunder Bay District, Ontario, Canada. It is about 750m (2,460feet) long and 100m (300feet) wide, and lies at an elevation of 390m (1,280feet). The primary inflow and outflow is the Whitesand River.