Lake Nemi is a small circular volcanic lake in the Alban Hills 30 km (19 mi) south of Rome in the Lazio region of Italy. It takes its name from Nemi, the largest town in the area, which overlooks it from a height.

The Alban Hills are the caldera remains of a quiescent volcanic complex in Italy, located 20 km (12 mi) southeast of Rome and about 24 km (15 mi) north of Anzio. The 950 m (3,120 ft) high Monte Cavo forms a highly visible peak in the centre of the caldera, but the highest point is Maschio delle Faete approximately 2 km (1.2 mi) to the east of Cavo and 6 m (20 ft) taller. There are subsidiary calderas along the rim of the Alban Hills that contain the lakes Albano and Nemi. The hills are composed of peperino, a variety of tuff that is useful for construction and provides a mineral-rich substrate for nearby vineyards.