The cast of “Vikings” season 1 is led by Travis Fimmel as Ragnar Lothbrok, Katheryn Winnick as Lagertha, Clive Standen as Rollo, and Gabriel Byrne as Earl Haraldson. The series also features Jessalyn Gilsig as Siggy, Gustaf SkarsgĂ„rd as Floki, George Blagden as Athelstan, and Alyssa Sutherland as Princess Aslaug. “Vikings” season 1 was filmed in Ireland and Canada.