Altenau is a town in Lower Saxony.
Altenau may also refer to: Altenau (Oker), a tributary of the Oker in eastern Lower Saxony Altenau (Alme), a tributary of the Alme in eastern North Rhine-Westphalia Altenau, a part of Mühlberg, Brandenburg, Germany
People with the surname Cornelis Altenau (died 1558), Danish-German builder
See also Altnau Altena (disambiguation) Altona (disambiguation)