Wenigerweiher, Protected lake in St. Gallen, Switzerland.

Wenigerweiher is an artificial reservoir at 838 m above sea level in the south-east of St. Gallen, between St. Georgen and Speicher. It is fed and crossed by the Steinach, which later flows into Lake Constance. A small island lies in the north-east of the lake, and its dam is the oldest functioning dam in Switzerland.

The lake was created between 1821 and 1823 by the merchant Michael Weniger, who founded his firm Michael Weniger & Comp. in 1815 and needed water power for his textile and metal businesses even in dry periods. Neighbouring companies paid him rent to use the reservoir. After his death in 1836 it stayed in family hands, administered by a foundation. In 1974 the lake was drained shortly before the amphibians' spawning season, prompting the St. Gallen nature conservation association to campaign for protection; the Schutzverordnung Wenigerweiher came into force in 1979, making it the city's first nature reserve. In 2002 the St. Gallische Naturwissenschaftliche Gesellschaft bought the lake and later built extra amphibian ponds in 2006.

The lake serves as a vital breeding ground for amphibians and plays an important role in the region's natural balance. Walking around it, visitors gain insight into why this place matters for protecting local wildlife habitats.

The lake is accessible via forest walking paths from the surrounding area, taking roughly 20 to 30 minutes on foot. Wear sturdy shoes and watch your footing, as the routes pass through undeveloped terrain with natural ground.

The lake holds one of Switzerland's highest-altitude populations of the water frog, and the pond frog found here is classed as strongly endangered in the country. The St. Georgenstrasse beside the water is closed to traffic during the amphibians' spring migration.