Álafoss (Icelandic pronunciation: [ˈauːlaˌfɔsː]; eel falls) is a waterfall on the river Varmá in Mosfellsbær, Iceland.

A wool factory of the same name has adjoined the waterfall since 1896, when a local farmer imported machinery to process wool using the energy from the waterfall.

During World War II, barracks were constructed there for British soldiers.

Álafoss played a major role in the founding and growth of the town of Mosfellsbær.

The band Sigur Rós has a studio named Sundlaugin at Álafoss, and the otherwise untitled fifth track on the band's album ( ) is nicknamed after the area.