| Allerbach | |
| Pushpin Map: | Saxony-Anhalt |
| Pushpin Map Caption: | Location of mouth in Saxony-Anhalt |
| Subdivision Type1: | Country |
| Subdivision Name1: | Germany |
| Subdivision Type2: | Region |
| Subdivision Name2: | Harz |
| Subdivision Type3: | State |
| Subdivision Name3: | Saxony-Anhalt |
| Length: | 50NaN0 |
| Source1 Location: | (see description) |
| Source1 Elevation: | ca. |
| Mouth Location: | (see description) |
| Mouth Elevation: | ca. |
| Custom Label: | References |
| Extra: | Its entire course is part of the Harzer Bachläufe nature reserve. |
The Allerbach is a tributary of the Warme Bode in the Harz Mountains of central Germany. It is just under 5km (03miles) long.
The source region of the "Little Allerbach" (Kleiner Allerbach) is in a boggy wood at a height of and lies about 100m (300feet) north of the level crossing on the K 1353 county road (Kreisstraße) (Sorge – Elend section) with the railway line of the Trans-Harz Railway.
The source region of the "Big Allerbach" (Großer Allerbach) is on the southwest hillside of the Rauher Jakob ; it lies at a height of .
The stream flows downhill in an easterly direction.
Regarding its confluence immediately next to the L 98 Landesstraße (Tanne – Königshütte section), the Allerbach forms the historic boundary of the Amt of Elbingerode. Even today there are numerous boundary stones left and right of the stream banks.