The Aller is a 215-kilometre-long (134 mi) river in the states of Saxony-Anhalt and Lower Saxony in Germany. It is a right-hand, and hence eastern, tributary of the Weser and is also its largest tributary. Its last 117 kilometres (73 mi) form the Lower Aller federal waterway. The Aller was extensively straightened, widened and, in places, dyked, during the 1960s to provide flood control of the river. In a 20-kilometre-long (12 mi) section near Gifhorn, the river meanders in its natural river bed.

Wolfsburg is the fifth largest city in the German state of Lower Saxony, located on the river Aller. It lies about 75 km (47 mi) east of Hanover and 230 km (143 mi) west of Berlin.