List of longest-lasting empires

This article is a list of longest-lasting empires organized according to their length of existence. An empire is a state that extends dominion over populations distinct culturally and ethnically from the culture/ethnicity at the center of power. Existence of each empire calculated from when the culture/ethnicity of power took control until that same power lost control of its empire. Start and end dates for empires often cannot be established in an objective manner being the subject of substantial scholarly debate. For example, according to the most generous interpretation one could argue that the Roman Empire began in the third century BC when Rome conquered substantial territories beyond the city and ended in the twentieth century AD when the Ottoman Empire, which claimed the Roman throne, was disbanded (most scholars, however, do not subscribe to this interpretation). In general some empires are assigned start dates beginning with when the state came into being according to some authority. Others begin not when the state emerges, but when the culture/ethnicity of power emerges. End dates can be variously assigned based on events as varied the conclusion of a key battle to a particular change in leadership. For the convenience of the reader, this article uses the date when the people at the center of power were no longer in formal control of the state due to being overthrown or placed in a position of vassalage to another authority. But even this specific definition is open to some debate among scholars.