Isaac Asimov stated explicitly that the Galactic Empire whose fall is depicted in his Foundation Series is modeled on the Roman Empire.
Ottoman Empire | Order of the British Empire | Russian Empire | Roman Empire | British Empire | Holy Roman Empire | German Empire | Byzantine Empire | Mughal Empire | Austrian Empire | First French Empire | Empire of Japan | Empire State Building | Vijayanagara Empire | Spanish Empire | Boardwalk Empire | Empire | Mongol Empire | Second French Empire | Order of the Indian Empire | Portuguese Empire | Achaemenid Empire | Parthian Empire | Maratha Empire | Western Roman Empire | Seleucid Empire | The Empire Strikes Back | Hackney Empire | The History of the Decline and Fall of the Roman Empire | The Cat Empire |
The Galactic Empire's Grand Admiral Thrawn, of the Timothy Zahn novels, is one such science fiction character who held this highest of naval ranks.
Within the Galactic Empire, based on mid 19th century Prussia, an ambitious military genius, Reinhard von Müsel, is rising to power.
Zub is in the employ of Emperor Zub of the Zub galactic empire who has been tasked with retrieving the Green Eye of Zub.