The thesis defended in this contribution to Viking studies in the British Isles is simple and straightforward. It is argued that the Viking warrior Ragnarr Loðbrók was an historical personage. Tradition associates him with the area about the Kattegat and in particular with south Norway and Zealand where Ragnarr and his sons were the leaders of a large force of vikings. These were sea-kings rather than rulers of territories. Ragnarr flourished in the first half of the ninth century and died some time after 851. Amongst his many sons, three were famous: Ívarr inn beinlausi, Hálfdan and Ubbe. Ragnarr was the leader (or one of the leaders) of the Danish attack on the Irish Vikings, probably Norwegians, in 851 and his son Ívarr established himself as king of Dublin which he ruled jointly from 853 with one Óláfr, identical with the Vestfold king, Óláfr Geirstaðaálfr, who after years of campaigning in Ireland with Ívarr returned to Norway in or about 871.