Neutral
- Orlando, the Duke of Oxford: An aristocrat, spy network leader and founding Kingsman Arthur.
- Pollyanna “Polly” Wilkins / Galahad: A maid, member of Orlando’s spy network and founding Kingsman Galahad.
- Captain Max Morton/The Shepherd: Posing as an English officer in the British Army, in reality a Scotsman seeking Scottish independence, the leader of a plot to pit the German, Russian, and British empires against each other. The character is based on Frederick Duquesne.
- Conrad Oxford: Orlando’s son, who switches places with a soldier Archie Reid to fight in the Great War against his father’s wishes.
- Erik Jan Hanussen: An occultist and the Shepherd’s third-in-command.
- Shola/Merlin: A butler, member of Orlando’s spy network and founding Kingsman Merlin.
- Mata Hari: An agent of the Shepherd and seducer of Woodrow Wilson.
- Rita
- Adolf Hitler: An assassin recruited by Hanussen.
- Emily Oxford: Orlando’s deceased wife and Conrad’s mother.
- Sergeant Major Atkins
- Archduke Franz Ferdinand of Austria
- Sophie, Duchess of Hohenberg
- Huge Machinery Shack Guard
- United States Ambassador/Bedivere
- Archie Reid/Lancelot
- Gavrilo Princip
- Alfred I. du Pont
Sweden
- Government
- Hjalmer Hammarskjöld and his Government
- Carl Swartz and his Government
- Nils Edén and his Government
- Swedish Monarchy
- Far Left
Allies
- Allied leaders of World War I
- United Kingdom
- Australia and New Zealand
- United States
- Italy
- Kingdom of Hejaz
Central Power
- Leaders of the Central Powers of World War I
- Ottoman Empire
- German Empire
