The Brunnenbach is a long, right-hand tributary of the Warme Bode, which flows to the west and south of Braunlage in Goslar district in the north German state of Lower Saxony.
Shortly after its source the Brunnenbach is impounded by the Silberteich reservoir, before it continues in a southeasterly direction past the Mutter-Kind-Heim Waldmühle, a mother-and-child centre, and local campsite. It then passes the forest inn of Forellenteich and the forest youth centre of , before finally turning east. The Brunnenbach is one of the most important tributaries of the Warme Bode. From its source to its mouth, the Brunnenbach descends some 220 meters in its 12 km journey.