Aldeyjarfoss is a waterfall in the Icelandic highlands. It is located at the northern end of Sprengisandsleið .

The waterfall is very attractive because of the contrast between the black basalt columns surrounding it and the foaming white water. In this respect, it is reminiscent of the much smaller Svartifoss in Skaftafell National Park.

The Skjálfandafljót river plunges some 20 metres[1] into the depths here. The basalt is part of a lava field called Frambruni, which is called Suðurárhraun in the southern part. A pseudo-crater was also cut by the river.