a river of N.W. Germany, rises in Eichsfeld, flows N. by W. through Prussian, Brunswick, and Hanoverian territories, receives on its right the Rhume and Innerste, on its left the Kaspan, and joins the Aller (a tributary of the Weser) on the left, near Hudemühlen, after a course of about 130 miles. The chief town on its banks is Hanover, where the river becomes navigable.