Heisterholz, Nature reserve in Petershagen, Germany.

Heisterholz is a protected nature reserve featuring oak woodlands, wetland areas, and creek valleys set on sandy soils. Spring-fed areas scattered throughout create distinct zones where water naturally emerges and supports different plant and animal communities.

The forest has long belonged to the state of North Rhine-Westphalia, and roughly half of its 880 hectares is now protected: a 403-hectare nature reserve listed as MI-064 and an FFH area of about 467 hectares (number 3619-301). The protection targets old oak woods on sandy soils, alder and ash swamps, and spring-fed hollows.

The forest gave its name to the former Heisterholz clay industry, which mainly made bricks and roof tiles. Its floor mosaic in the Kaiser-Wilhelm-Gedächtniskirche in Berlin was also a Heisterholz product. The woodland belongs to the state of North Rhine-Westphalia.

The forest lies southwest of Petershagen's core, bounded by the B61 to the east and the L770 and L772 to the north; the western and southern edges follow the woodland rim. The roughly 403-hectare nature reserve (code MI-064) sits within the 880-hectare wood and borders the Nordholz and Kohbrink reserves near Todtenhausen. The whole area belongs to the state of North Rhine-Westphalia.

The forest takes its name from the former Heisterholz clay industry, which made bricks and roof tiles there; its floor mosaic in Berlin's Kaiser Wilhelm Memorial Church came from this works. The 403-hectare nature reserve, designated MI-064, lies within a roughly 880-hectare woodland owned by the state of North Rhine-Westphalia.