"Revenge" is the eighteenth episode of the fourth season of Vikings. It is the forty-seventh episode of the series overall. It first aired on January 18, 2017. It was written by creator Michael Hirst and directed by Jeff Woolnough.
Ragnar's plan comes to fruition; the Viking army lands on the coast of Northumbria.
As the great army assembles, Bjorn and Ivar fight over leadership of the army. Harald spots the woman he fell in love with years ago, Ellisif, which made him want to conquer Norway to impress her. To his anger, she has married a danish earl, a man of lower status than him. Ubbe and Margrethe are married, but Ubbe agrees to share his bride with Hvitserk. Helga wants to join the great army, but Floki is against it. Floki admits being confused about his worldview. Harald and Halfdan has Egil infiltrate Kattegat. Halfdan suggests Harald kill Ellisif to regain his honor, but Harald refuses because she is the only woman he loves. Earl Jorgensen volounteers as a sacrifice to assure victory in the coming war, while Bjorn and Astrid continue their affair. Athelwulf confronts Ecbert about his affair with Judith and questions Ecbert's love for him and his ability as a king. Ecbert claims he used Athelwulf because he had complete trust in him and asks him to lead their defences against the coming attack. As the great army lands in England, king Aella faces them, but his meagre army is overrun. Aella is captured and submitted to the blood eagle.
- Katheryn Winnick as Lagertha
- Gustaf Skarsgård as Floki
- Alexander Ludwig as Bjorn
- John Kavanagh as The Seer
- Peter Franzén as King Harald "Finehair"
- Jasper Pääkkönen as Halfdan "The Black"
- Moe Dunford as Prince Aethelwulf
- Alex Høgh as Ivar
- Marco Ilsø as Hvitserk
- David Lindström as Sigurd
- Jordan Patrick Smith as Ubbe
- Linus Roache as King Ecbert
Special Guest Star
- Josh Donaldson as Hoskuld
- Josefin Asplund as Astrid
- Maude Hirst as Helga
- Ivan Kaye as King Aelle
- Ida Marie Nielsen as Margrethe
- Georgia Hirst as Torvi
Additional Cast (in order of appearance)
- Charlie Kelly as Egil
- Anton Gitrap as Guthrum
- Sophie Vavasseur as Princess Ellisif
- Gary Buckley as Earl Vik
- Noni Stapleton as Pagan Priestess
- Sinead Gormally as Tanaruz
- Jack Nolan as Earl Jorgensen
- Niall O'Sioradain as Priest of Uppsala (as Pagan Priest)
- David Maine as Royal Servant
- Gary Murphy as Bishop Unwan
- Cathy White as Ealhswith
- Caitlin Scott as Blaeja
- This episode features an appearance from Toronto Blue Jays third baseman Josh Donaldson.
- This episode marks the death of King Aelle.