Hrolleifsdalur is a valley that leads from Sléttuhlíð on the east side of Skagafjörður, Iceland heading to the southeast end of Tröllaskagi mountain range.

[1] The valley is said to be named after the settler Hrolleifur mikli Arnhallsson.

[2] The Hrolleifsdalsá river runs through the valley and then into the ocean in the southern part of Sléttuhlíð.

[1] Hrolleifsdalur has been protected for many years, but there have been difficulties because of many heavy snows in the valley.

There is a small amount of geothermal energy in Hrolleifsdalur and a lake that formed in a borehole on the land of the abandoned farm Bræðraá, which now leads to Hofsós.