Bommer Weiher, Protected lake system in Kemmental, Switzerland.

Bommer Weiher is a protected lake system consisting of several connected fish ponds in the Kemmental region of Thurgau canton. The waters cover approximately 15 hectares at about 530 meters in elevation and are surrounded by reed beds and forest.

The ponds were established around 1460 as water reservoirs and fish breeding grounds for local needs. Over time they transitioned from production sites into a nature reserve.

The site reflects how water resources and habitats are managed in Switzerland through shared responsibility between organizations and private landowners. Visitors can see how traditional land use and nature protection coexist here.

A marked trail runs through the pond area, crossing the Fortibach, which flows through the ponds from east to west. The ponds themselves may no longer be used, though fishing is still permitted on a very limited basis. The site is owned in equal thirds by private individuals, the canton of Thurgau and Pro Natura.

The ponds were dug in 1460 on the orders of the Great Hospital of Konstanz, as recorded in a parish register of Alterswilen; local lore credits the Bishop of Konstanz instead. Ownership is split equally between private owners, the canton of Thurgau and Pro Natura, which received its third through a legacy in 2003.