In the far future, most of the known galaxy is despotically ruled by the revolving triumvirate of Emperor Cleon's clones: Brother Day, a Cleon in his prime; Brother Dusk, a retired and aging Cleon who serves in an advisory role; and Brother Dawn, a young Cleon being trained to succeed Brother Day. This "genetic dynasty" has been surreptitiously administered for 400 years by the regal Lady Demerzel, the emperor's majordomo and secretly a unique, ageless humanoid robot. Young Gaal Dornick solves a complex mathematical proof and wins a galaxy-wide contest, devised by famed mathematician and psychology professor Hari Seldon to find another mind capable of understanding his work.

Arriving on the capital planet Trantor, Gaal is thrust into the center of a conflict between the Cleonic dynasty and Seldon’s schools surrounding the merits of psychohistory, an algorithm created by Seldon to predict the events and actions of large masses of people across vast timelines. With Gaal to verify his findings, Seldon explains and publicly forecasts the decay and imminent fall of the empire, which cannot be averted, but the consequences of which may be mitigated by the creation of a Foundation to preserve the collective knowledge and innovations of humanity. The Cleons, known collectively as Empire, are initially dismissive of Seldon, but following the first of a series of predicted catastrophic events leading to the fall, tentatively allow him and his followers to establish the Foundation in exile: on the remote planet Terminus. The series chronicles Empire's subsequent conflicts with the flowering Foundation and its allies over the course of the passing centuries, as well as the characters which bridge the divide between them.