| Lac de Saint-Agnan | |
| Location: | Nièvre |
| Pushpin Map: | France |
| Coords: | 47.3286°N 4.0892°W |
| Type: | artificial |
| Inflow: | Cousin, Trinquelin |
| Outflow: | Cousin |
| Basin Countries: | France |
| Length: | 2.5km (01.6miles) |
| Width: | 0.5km (00.3miles) |
| Area: | 1.4km2 |
| Elevation: | 560m (1,840feet) |
Lac de Saint-Agnan is a lake in Nièvre, France. At an elevation of 560 m, its surface area is 1.4 km2.
It was inaugurated in 1969. It is the last of the great lakes born from the Morvan dam. The lake was drained in October 2002 and 2008.