The River Aln runs through the Alnwick district of the County of Northumberland in England, discharging into the North Sea on the east coast of England.

The river gives its name to the town of Alnwick and to the village of Alnmouth, and its source is in Alnham in the Cheviot hills. The Aln is a relatively small river but has been important through history as one of the boundaries along which English and Scottish troops marching to war had to cross; for that reason, it was at times heavily defended.

See also

• Rivers of the United Kingdom