The Styrdalen dolmen (also known as Hjälteby Round Cairn; RAÄ Valla 15:1) is located to the west of Valla and north of Vallhamn and Habborsby on the island of Tjörn in the province of Bohuslän, Sweden.
The dolmen is situated on a hill approximately ten meters in diameter, right next to the road Hjältebyvägen from Valla church to Furusäter. Four support stones and an overhanging flat capstone create a mushroom-shaped small chamber. There are cup marks on the capstone (15) and one of the support stones. The dolmen was excavated and restored in 1915.