Siward Barn (Old English: Sigeweard Bearn) was an 11th-century English thegn and landowner-warrior. He appears in the extant sources in the period following the Norman Conquest of England, joining the northern resistance to William the Conqueror by the end of the 1060s. Siward's resistance continued until his capture on the Isle of Ely alongside Æthelwine, Bishop of Durham, Earl Morcar, and Hereward ("the Wake")as cited in the Anglo-Saxon Chronicle.