Altenau
Altenau ford near Küblingen
Location of mouth in Lower Saxony
Location
Country	Germany
State	Lower Saxony
Reference no.	DE: 4826
Physical characteristics
Source
• location	northeast of Eitzum in the Elm
• coordinates	52°10′08″N 10°51′17″E / 52.16889°N 10.85472°E / 52.16889; 10.85472
• elevation	about 206 m
Mouth
• location	Oker near Wolfenbüttel
• coordinates	52°08′10″N 10°33′24″E / 52.136175°N 10.556703°E / 52.136175; 10.556703
• elevation	77 m
Length	25.0 km (15.5 mi) [1]
Basin size	140 km2 (54 sq mi) [1]
Basin features
Progression	Oker→ Aller→ Weser→ North Sea
Landmarks	Small towns: Schöppenstedt
Tributaries
• left	Rothebach
• right	Sauerbach, Hachumerbach, Glue Riede

The Altenau is a small river of Lower Saxony, Germany. It rises in the Elm, northeast of Eitzum [de], a district of Schöppenstedt, and discharges from the right into the Oker near Halchter [de], a district of Wolfenbüttel.

Between the heights of the Asse and the Heeseberg in the south and the Elm ridge in the north stretches an almost treeless arable plain, the roughly 25 kilometre long Schöppenstedt Depression (Schöppenstedter Mulde). Here the Altenau flows in an east-west direction in a meadow valley about 500 metres wide. The source of the river lies immediately west of the watershed between the rivers Weser and Elbe. In the southern part of the depression the Altenau picks up a succession of small streams from the slopes of the Elm as it cuts through the hollow as a regulated and relatively straight stream.

• List of rivers of Lower Saxony

• Altenau valley (in German)
• TU Berlin Project Altenau^{[permanent dead link‍]} (in German)
• Excursions (in German)