Gigerwaldsee is a reservoir in the Calfeisental valley, located in the municipality of Pfäfers , Canton of St. Gallen , Switzerland. The reservoir has a volume of 35.6 million m³ and covers a surface area of 71 ha (180 acres).

The reservoir was formed by the arch dam Gigerwald, which was completed in 1976, standing at a height of 147 m.