Who are the main characters in the History Channel's Vikings series?

The main characters in the "Vikings" television series include, Ragnar, Lagertha, Rollo, Floki, Siggy and Athelstan through season three. The main characters for season four may change due to events that occurred in the end of season three.

Ragnar Lothbrook, who has gone from fighter, to Jarl and finally to the King of his people, is played by Travis Fimmel. His first wife and mother of his first two children, Lagertha is played by Katheryn Winnick. Rollo, Ragnar's brother, is played by Clive Standen. The relationships in the show between these three and their lives are part of the main focus of the show even though they aren't the only main characters of the show.