Galactic empire

A Galactic Empire is a multi-ethnic (or in this case commonly multi-species) or multi-national state spanning an entire galaxy with political and/or military dominion over it's citizens who are culturally or ethnically (in this case commonly species) distinct from the ruling (Imperial) ethnic or species and it's cultural group. The capital of a Galactic Empire is typically a planet near to the center of the galaxy it governs for efficiency sake. Some Empires of lesser territory have called themselves by such name upon claiming most of the galaxy.

The example most known to the public is perhaps the Galactic Empire of the Star Wars franchise.