Schultheisweiher, Natural lake and recreation area in Offenbach am Main, Germany.

Schultheisweiher is a 10.4-hectare lake in the Mainbogen between Offenbach-Bürgel and Offenbach-Rumpenheim, dug in 1928 as a gravel pit by the Schultheis company. Its southern half serves bathers, model-boat sailors and anglers, while the northern half is a fenced-off biotope for rare birds. The west bank has a large sunbathing lawn with a small nudist area, showers and sanitary facilities.

The Schultheis company dug the pit in 1928; gravel extraction ended in the 1960s, after which parts of the site were filled with waste until authorities banned this in 1975. In the late 1970s Cassella handed the area to the Umlandverband Frankfurt, which turned it into a recreation area. The surrounding Rumpenheimer und Bürgeler Kiesgruben were designated a nature reserve on 23 March 1983.

The lake is a popular spot for families and young people from Offenbach who come to picnic and sunbathe along the shore. On warm days, it draws a mixed crowd from the surrounding neighborhoods.

There is no car park directly at the lake; vehicles may drive up close to the water only to stop briefly and load or unload. Bathers are supervised from 10:00 to 20:00 during the May to September season, and swimming outside those hours is prohibited. Walkers and cyclists from Frankfurt-Fechenheim reach the site via the Arthur-von-Weinberg footbridge.

A phosphate removal system installed in 2022 works automatically to keep the water's ecological balance stable. Systems like this are still uncommon at urban bathing lakes in Germany.