Zillierbach Dam, Gravity dam near Elbingerode, Germany.

Zillierbach Dam is a concrete gravity dam built 1934–1936 in the East Harz, about 3 km southwest of Voigtstieg. Its 186.5 m long, 3.5 m wide crest stands at 473.8 m above sea level and rises roughly 45 m above the foundation. It impounds the Zillierbach into a reservoir about 24 ha in size and 1.4 km long, with a small wooded island near the southern shore that becomes a walkable peninsula at low water.

The plan for a dam at the Zillierbach arose in 1931; construction ran from 1934 to June 1936, first intended as an arch dam but built as a concrete gravity dam. Material arrived by a works railway from Drei Annen Hohne, and a sawmill was built at the reservoir inlet for the formwork timber. In 1935 workers found a Bronze Age hoard from around 1000 BC below the Peterstein, now in the Harzmuseum Wernigerode. In the war's final days the SS planned to blow up the wall, which the dam master's warning to the Allies prevented.

The stream was called Holtemme until the 16th century and appears as Zilgerbach from 1558; the present name came later. Its uneven flow was regulated by the Wormsgraben, an artificial ditch on the south side of the Hohneklippen built in the late 12th century. The reservoir lies in a drinking water protection area, so swimming is not allowed.

A 4.5 km circular trail circles the reservoir and crosses the dam crest, which has been open to walkers since the 1998–2000 overhaul. Access is from Drei Annen Hohne, Elbingerode or Wernigerode. A side path climbs to the Peterstein (498 m), where trees were cleared to open the view over the dam and lake. Swimming in the reservoir is forbidden because it is a drinking water protection area.

The water body was previously known by a different name and originally served to supply water to several settlements in the Harz. This function remains important today for providing drinking water to the region.