Travis Fimmel Ragnar Lothbrok Actor Gustaf Skarsgård Floki Actor Katheryn Winnick Lagertha Actor Jessalyn Gilsig Siggy Actor George Blagden Athelstan Actor Clive Standen Rollo Actor Alexander Ludwig Bjorn Actor Alyssa Sutherland Princess Aslaug Actor Linus Roache King Ecbert Actor Ben Robson Kalf Actor Kevin Durand Harbard Actor Lothaire Bluteau Emperor Charles Actor Morgane Polański Princess Gisla Actor Ivan Kaye King Aelle Guest Star Michael Hirst Executive Producer Morgan O'Sullivan Executive Producer John Weber Executive Producer Sherry Marsh Executive Producer Alan Gasmer Executive Producer James Flynn Executive Producer Sheila Hockin Executive Producer