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.
Doubt has been cast on his connection with Sigurd Rise, a relatively obscure son of Harald Fairhair by a Sami girl named Snæfrithr Svásadottir.
According to the Heimskringla, "King Olaf Tryggvason came to Ringerike to spread Christianity, Sigurd Syr and his wife allowed themselves to be baptized".
In 1014, he successfully petitioned his peers, the other Norwegian local kings, for their support in his stepson's cause when Olav wanted to build an army in Norway.