Ivar the Boneless (; ) was a Viking leader and a commander of the Great Heathen Army which invaded the Anglo-Saxon kingdoms of England, starting in 865. According to the tradition recorded in the Norse sagas, he was one of the sons of Ragnar Lothbrok, and his brothers included Björn Ironside, Halfdan Ragnarsson, Sigurd Snake-in-the-Eye and Ubba. He is often considered identical to Ímar, the founder of the Uí Ímair dynasty, which dominated the Irish Sea region throughout the Viking Age.