Lac d'Emosson is a reservoir in the canton of Valais, Switzerland. It is located in the municipalities of Salvan and Finhaut. The closest major city in Switzerland is Martigny. The lake has a surface area of 3.27 km² and an elevation of 1,930 m. The maximum depth is 161 m.

The first dam of Emosson (also known as Barberine Dam) was built in 1925. The current dam with a height of 180 m was completed in 1974 and floods the old dam. It increased the reservoir's volume from 40 mio m³ to 227 mio m³. The old dam can still be seen when the water level in the Lac d'Emosson is very low.

To reach the dam a funicular railway is used, which is the steepest 2-cabin funicular railway in the world with a gradient of 87 percent.