Games like Undead Overlord
Games like Undead Overlord include Infection Free Zone, Plague Inc: Evolved, They Are Billions, Touhou Big Big Battle, and Cepheus Protocol. We matched them by the tags players give Undead Overlord on Steam (Strategy, Indie, Early Access, Zombies, and RTS): closest matches first, and among equally close ones the better-known games.

Infection Free Zone
Shared: Strategy · Zombies · RTS

Plague Inc: Evolved
Shared: Strategy · Indie · Zombies

They Are Billions
Shared: Strategy · Zombies · RTS

Touhou Big Big Battle
Shared: Strategy · Early Access · Indie

Cepheus Protocol
Shared: Zombies · RTS · Strategy

Plants vs. Zombies GOTY Edition
Shared: Strategy · Zombies · Indie

Rusted Warfare - RTS
Shared: Strategy · RTS · Indie

Circle Empires
Shared: Strategy · Indie · RTS

Zombie Night Terror
Shared: Strategy · Zombies · Indie

MarZ: Tactical Base Defense
Shared: Strategy · Indie · RTS

Wargame: Red Dragon
Shared: Strategy · RTS · Indie

Creeper World 3: Arc Eternal
Shared: Strategy · Indie · RTS

Tooth and Tail
Shared: Strategy · Indie · RTS

Slay the Spire 2
Shared: Strategy · Indie · Early Access

Shadow Tactics: Blades of the Shogun
Shared: Strategy · Indie · RTS

Organ Trail: Director's Cut
Shared: Indie · Strategy · Zombies

Age of Empires II (Retired)
Shared: Strategy · RTS

RIOT: Civil Unrest
Shared: Strategy · Indie · RTS

Risen Kingdom
Shared: Strategy · Indie · RTS

Invasion Machine
Shared: Strategy · Indie · RTS

Dead State: Reanimated
Shared: Zombies · Strategy · Indie

Diplomacy is Not an Option
Shared: Zombies · RTS · Strategy

Buoyancy
Shared: Strategy · Indie · Early Access

Battle Realms: Zen Edition
Shared: Strategy · RTS · Early Access