The Imperium of Man is a fictional galactic empire

Galactic empire

Galactic empires are a common trope used in science fiction and science fantasy, particularly in space opera. Many authors have either used a galaxy-spanning empire as background, or written about the growth or decline of such an empire...

 of over a million planets that contains the vast majority of humans in the forty-first millennium, set in the Warhammer 40,000

Warhammer 40,000

Warhammer 40,000 is a tabletop miniature wargame produced by Games Workshop, set in a dystopian science fantasy universe. Warhammer 40,000 was created by Rick Priestley in 1987 as the futuristic companion to Warhammer Fantasy Battle, sharing many game mechanics...

universe created by Games Workshop

Games Workshop

Games Workshop Group plc is a British game production and retailing company. Games Workshop has published the tabletop wargames Warhammer Fantasy Battle and Warhammer 40,000...

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Fictional background

In the fiction, the Imperium is depicted as a loose empire, nominally consisting of all human-inhabited worlds in explored space and united through imposed religious conviction, extreme xenophobia, militarism, fascism, despotic hierarchical rule, and threats of brutal disciplinary force. The founder of the Imperium, an enigmatic and mysterious persona known only as the 'Emperor of Mankind' is in theory the supreme ruler of this galaxy-spanning empire, although in practice the highest tier of command is the supreme council known as the High Lords of Terra, based on Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, who have ruled for ten millennia under the Emperor's name, as the Emperor lays dormant on the Golden Throne in a nearly unresponsive state of hyper-focused attention to maintaining, among other things, the Astronomicon, a psychic navigational beacon dependent upon his powers alone.