
- Travis Fimmel as King Ragnar Lothbrok, the head of the Viking Earldom of Kattegat who became king after Horik's death.
- Katheryn Winnick as Lagertha, a shieldmaiden and Ragnar's ex-wife; she controls the Earldom of Hedeby calling herself Earl Ingstad.
- Clive Standen as Rollo, a warrior and Ragnar's brother; the character is based on the historical person who was the great-great-great-grandfather of William the Conqueror..
- Jessalyn Sarah Gilsig as Siggy, widow of the late Earl Haraldson and Rollo's lover.
- Gustaf Skarsgård as Floki, a gifted shipbuilder and friend of Ragnar's.
- George Blagden as Athelstan, an Anglo-Saxon monk from Northumbria who is torn between the Viking gods and the Christian God; he is a friend and adviser to both King Ragnar and King Ecbert.
- Alexander Ludwig as Björn Ironside, Ragnar and Lagertha's son, who has fallen in love with the shieldmaiden Þórunn.
- Alyssa Sutherland as Queen Aslaug, Brynhildr 's daughter and Ragnar's second wife.
- Ben Robson as Kalf, the ruler of Hedeby in the absence of Lagertha.
- Kevin Durand as Harbard, the "Wanderer".
- Lothaire Bluteau as Emperor Charles.
- Linus Roache as King Ecbert of Wessex, the ruthless king of Wessex.