Vallhólmur, also called Hólmurinn, is a flatland area in the middle of Skagafjörður, Iceland, formed from sediment from the Héraðsvötn river—it is in fact an old seabed.

The area's eastern boundary is the Héraðsvötn and Húseyjarkvísl,[1] and its western is Vindheimamelar.

[2] The region is flat and level except for two hills that rise up from the plain, Skiphóll and Vallholt.

There are two farms with the same name, Syðra- and Ytra-Vallholt (South- and Far Vallholt), up against the back of Vallholt, and a short distance from Vallalaug spring, which is often mentioned in the Sturlunga saga and other sources from that era.

This suggests that the Héraðsvötn previously ran further west, at least intermittently.