| Lake Ptuj | |
| Pushpin Map: | Slovenia |
| Location: | Drava |
| Coords: | 46.4019°N 15.8933°W |
| Basin Countries: | Slovenia |
| Length: | 5500m (18,000feet) |
| Width: | 1600m (5,200feet) |
| Area: | 3.5km2 |
| Max-Depth: | 12m (39feet) |
| Volume: | 0.02km3 |
| Elevation: | 217.5m (713.6feet) |
| Islands: | 2 |
| Cities: | Ptuj |
Lake Ptuj (in Slovenian pronounced as /ˈptuːi̯/; Slovenian: Ptujsko jezero) is a reservoir on the Drava River southeast of the town of Ptuj in eastern Slovenia. It is the largest reservoir in Slovenia and was created in 1978 when a dam for the Formin hydroelectric power plant was built on the Drava. It is still used as the reservoir for the power plant, but is also popular for rowing, sailing, and fishing.