Dalasýsla was a county in Iceland, located in the Western Region region of the country. Its only town is Búðardalur.
The county had a rich history dating back to the first settlers of Iceland. Leif Erikson grew up in Dalasýsla in the 10th century, and Árni Magnússon, scholar and collector of manuscripts, was born at Kvennabrekka in Dalasýsla in 1663.
The poet, historian, and politician Snorri Sturluson was born at the farm of Hvammur í Dölum.