Games like The King's Campaign
Games like The King's Campaign include Europa Universalis IV, Crusader Kings III, Europa Universalis V, Hearts of Iron IV, and Age of History 3. We matched them by the tags players give The King's Campaign on Steam (Grand Strategy, RTS, 4X, Strategy, and Wargame): closest matches first, and among equally close ones the better-known games.

Europa Universalis IV
Shared: Grand Strategy · Strategy · 4X

Crusader Kings III
Shared: Grand Strategy · Strategy · Medieval

Europa Universalis V
Shared: Grand Strategy · Strategy · Historical

Hearts of Iron IV
Shared: Grand Strategy · Strategy · Historical

Age of History 3
Shared: Grand Strategy · RTS · Strategy

Crusader Kings II
Shared: Grand Strategy · Strategy · Medieval

Manor Lords
Shared: Strategy · Grand Strategy · Simulation

Sid Meier's Civilization VII
Shared: Grand Strategy · Strategy · 4X

Sid Meier’s Civilization® VI
Shared: Strategy · Grand Strategy · Historical

Farthest Frontier
Shared: Strategy · Building · Medieval

Total War: ROME REMASTERED
Shared: Grand Strategy · Strategy · RTS

Terra Invicta
Shared: Grand Strategy · Strategy · 4X

Workers & Resources: Soviet Republic
Shared: Strategy · Grand Strategy · Simulation

Knights of Honor II: Sovereign
Shared: Grand Strategy · Strategy · RTS

Total War: WARHAMMER
Shared: Strategy · Grand Strategy · 4X

Total War: MEDIEVAL II – Definitive Edition
Shared: Strategy · Grand Strategy · Medieval

Medieval Kingdom Wars
Shared: Grand Strategy · RTS · Medieval

Victoria 3
Shared: Grand Strategy · Strategy · Simulation

Victoria II
Shared: Grand Strategy · Strategy · Historical

Against the Storm
Shared: Strategy · Grand Strategy · Simulation

Stellaris
Shared: Grand Strategy · Strategy · 4X

Empires of the Undergrowth
Shared: Strategy · Grand Strategy · Simulation

Stronghold: Definitive Edition
Shared: Strategy · RTS · Medieval

Rebel Inc: Escalation
Shared: Grand Strategy · Strategy · 4X