Ivar "the Boneless" Ragnarsson is a character in The Last Kingdom by Bernard Cornwell. He was not present in the BBC series, though he was mentioned in "Episode 4" as having been killed while in Ireland.
Ivar is the older brother of Ubba and Halfdan and a son of the Danish-Swede king, Ragnar Lothbrok. He is one of the two co-leaders of the "Great Heathen Army" with Ubba during its early years. Where Ubba is aggressive and superstitious, Ivar is insightful and clever.
- The explanation for Ivar's epithet "the Boneless" (Old Norse: Ivar hinn Beinlausi) given in The Last Kingdom novel was on account of his skinny appearance. Another theory in respect to his nickname contends that Ivar may have suffered from Osteogenesis imperfecta, citing that Ivar was carried on a shield by his followers, even though this may have otherwise been due to his status as a chieftain.
- Ivar is believed to be the founder of the Norse-Gael Ui Imair dynasty which variously ruled over Dublin, the Isle of Mann and the Hebrides.