Sigurd Syr (Old Norse: Sigurðr Sýr) (died c. 1018) was a Norwegian petty king of Ringerike, a region in Buskerud. He was notable in Norwegian history largely through his association with Kings Harald Hardrada and Olaf II of Norway. By his marriage with Åsta Gudbrandsdatter after her first husband Harald Grenske had died, Sigurd Syr was stepfather of King Olaf II and the father of King Harald III.