Eystein Haraldsson (Old Norse: Eysteinn Haraldsson, Norwegian: Øystein Haraldsson); c.1125–1157) was king of Norway from 1142 to 1157. He ruled as co-ruler with his brothers, Inge Haraldsson and Sigurd Munn. He was killed in the power-struggle against his brother, Inge, in an early stage of the civil war era in Norway.