Through the centuries-spanning nature of the Foundation series, the lives of its various characters are limited to one or two of its nine episodes.: 2, 5 In spite of the great success of the series, its characters have been described as "undifferentiated and one-dimensional" speaking with an "impoverished vocabulary". Their consciousness "shows absolutely no historical development and hence fails to evoke in the reader any feeling for the future universe they inhabit". Characterization in general is subordinated to the overall conception of Asimov's project.
Through the eyes of the characters the inevitability of the forces of history, made manifest in the Seldon Plan, is demonstrated to the reader repeatedly. Charles Elkins sees the characters in Foundation not as "tragic heroes. They are nondescript pawns, unable to take their destiny into their own hands." Only those elite few characters who understand the Plan can be considered free, with the Mule through his non-human psychic powers as the only exception. But while Elkins attributes the Foundation series a sense of "pervading fatalism", Nicolas David Gevers and James Gunn point out that the obstacles presented in Asimov's galactic history are overcome by active individual characters "through the initiative and competence which the Foundations nurture in their citizens".: 56 : 44 Donald E. Palumbo asserts that it is exactly the "flatness of character and setting" which permit the series "to be a masterpiece".: 3 The heroism and depth of individual characters is consciously taken back by Asimov for the true hero of the series to stand out: "the sublime history of humankind itself".: 46
Future novelist Arcadia "Arkady" Darell is the "concluding key figure" of the original Foundation trilogy.
Ammel Brodrig is an influential courtier and Privy Secretary at the court of Cleon II. He is depicted as a particularly corrupt character, lacking even the elementary honesty of honourable corruption. Nicolas David Gevers saw Brodrig as based on Narses, an important member of the court of Byzantine emperor Justinian I, "who dogged Belisarius" - the model for Bel Riose - "and ultimately replaced him as general".: 57
Asimov loosely based Bel Riose on Flavius Belisarius, a great general of the Roman Empire during the 6th century AD. Like Riose, Belisarius served a strong emperor, Justinian the Great, in an empire that had declined from its peak (Belisarius was one of the people, along with Justinian,: 56–57 known as "the last of the Romans", i.e., imperials); helped it to recapture much of its lost territory, including Rome itself; and was called back on baseless suspicion that he was angling for the Imperial throne. Unlike Riose, Belisarius was not executed but retired (and, according to unsubstantiated legend, was blinded and cast out of Constantinople as a beggar).
James Gunn saw Riose as "the only character who stares in the face of determinism". While his failure against the forces of historic necessity might seem depressing, the fact that he is not the viewpoint character changes the impact of the story: the reader sympathizes with the Foundation. Riose's failure is depicted as desirable, as it ensures the Foundation's survival.: 42
Cleon II is the last strong monarch of the Galactic Empire. As the Galactic Empire is based on the Roman Empire, and Bel Riose is based on Belisarius, Cleon II is clearly based on the Eastern Roman Emperor Justinian I.: 57 His name however derives from Cleon, an Athenian politician of the Peloponnesian War (just as Eastern Roman emperors soon after Justinian used Greek names). In the 2021 TV adaptation, all Emperor Cleons are genetic clones of Emperor Cleon I, but this is not in Asimov's books, which do not include cloning.
Emperor Dagobert IX is one of the last emperors of the Galactic Empire.
Nicolas David Gevers pointed out the parallels between the character of Dagobert and the destitute last Western Roman emperor Romulus Augustulus. In this reading, the rebel Gilmer, the character responsible for the sack of Trantor, is equated with Alaric, king of the Visigoths.: 57
At face value, Venabili is a woman two years younger than Seldon, in her own words "not very good-looking". She tells Seldon that she is a historian from Cinna, and, before her involvement in The Flight, Venabili taught history classes at Streeling University on Trantor.
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Ebling Mis is a psychologist from Terminus, appearing in the second part of Foundation and Empire, who tried to reproduce Hari Seldon's psychohistory in order to reveal the Second Foundation and warn them about The Mule.
He is a young mathematician, newly awarded his Doctorate, and originates from Synnax. He has been invited to Trantor by Hari Seldon to join the psychohistory project. He meets Seldon shortly after arrival on Trantor, but is already under surveillance by agents of the Committee of Public Safety. Seldon reveals to him that psychohistory has predicted the fall of the Imperium to be unavoidable, and that exile to the remote planet of Terminus is in fact Seldon's real goal. Gaal is arrested and interrogated. He eventually moves to Terminus to continue Seldon's legacy.
Hari Seldon is the founder of the two Foundations. He is a psychohistorian who, through the calculations of psychohistory, predicts the downfall of 'The Empire' and a potential 30,000-year interregnum. He sets up the First and Second Foundations to reduce this huge gap from 30,000 years down to 1000 years. Following a trial, Hari Seldon and his 100,000 followers are exiled to the planet Terminus where the First Foundation is set up. Unknown to many, a Second Foundation is set up at a separate location. Clues to its existence come from a statement by Hari Seldon of it being at 'Star's End'. Many searches are made for this and several of the characters have their own theories about where this is.
Hober Mallow is one of the great heroes of the Foundation. He did not hail from the Foundation's home-planet of Terminus, but from Smyrno, a hot and dry planet, whose inhabitants are not held in high regard by foundation members. Master Trader Mallow (as he was titled at the time) caused a change in tides for the Foundation when he opened up trade with the Korelian Republic, offering them the nuclear gadgets of the Foundation, without the Korelians having to accept science as a religion, which was the usual Foundation requirement. After being exonerated after a trumped-up murder trial, he was elected Mayor of Terminus. While serving this role, he resolved the Korelian Crisis, by simple virtue of inaction, letting "the forces of history resolve the crisis". This inaction created a slow but growing turmoil, as Korelians' nuclear-powered devices started slowly degrading. The lack of service and replacements fomented economic revolt, over time. His influence moved the Foundation from an era where it used religion to spread its influence, to an era where trade was what primarily grew the reach of the Foundation. 
Homir Munn is a librarian and owns one of the biggest collections of information about the Mule.
Munn is one of five conspirators central to the plot of Second Foundation, who plan to find the location of the Second Foundation.
Homir Munn "is a stutterer described as "lanky," "ill-at-ease," and "introverted." Marcia J. Myers found that this "stereotype behavior gives this librarian's image an overall rather negative rating".
Jord Fara is a member of the board of trustees of the Foundation of the Encyclopedia Galactica in its early years. Fara weighs three-hundred pounds.
Lewis Pirenne is Chairman of the board of trustees of the Foundation of the Encyclopedia Galactica on Terminus, about fifty years after its establishment. Salvor Hardin eventually takes over when it is clear that the Foundation needs to be led by a politician rather than a scientist. Doubtless his name refers to the famous historian Henri Pirenne.
Limmar Ponyets is Master Trader of the Foundation who obtains Eskel Gorov's release by supplying the Askonians with a transmuter capable of converting iron into gold.
Lundin Crast is Member of the Board of Trustees of the Encyclopedia Committee.
Salvor Hardin is the first mayor of Terminus City, the sole inhabited location on the planet Terminus.
According to his autobiography In Memory Yet Green (1979), Asimov modeled the Mule's physical appearance on Leonard Meisel, a friend at the World War II-era Navy Yard in Philadelphia. In keeping with the Foundation series being based on the Roman Empire, the Mule has historical parallels with Attila the Hun,: 57 Tamerlane, and Charlemagne; he has also been compared to the Roman Emperor Augustus, Napoleon, Hitler, Stalin, and several other tyrants and demagogues of recent history.
Tomaz Sutt is Member of the Board of Trustees of the Encyclopedia Committee.
Yate Fulham is Member of the Board of Trustees of the Encyclopedia Committee.
Yohan Lee is one of Salvor Hardin's advisors and friends.
- Palumbo, Donald E. (2016). An Asimov Companion: Characters, Places and Terms in the Robot/Empire/Foundation Metaseries. Critical Explorations in Science Fiction and Fantasy. Vol. 51. Jefferson, North Carolina: McFarland & Company. ISBN 978-0-7864-9823-9.
- Elkins, Charles (March 1976). "Isaac Asimov's FOUNDATION Novels: Historical Materialism Distorted into Cyclical Psycho-History". Science Fiction Studies.
- Gevers, Nicholas David (August 1997). Mirrors of the past : versions of history in science fiction and fantasy (PhD). University of Cape Town. Retrieved 7 October 2021.
- Gunn, James (1982). Isaac Asimov: The Foundations of Science Fiction. Oxford University Press. ISBN 0-19-503060-5.
- Hassler, Donald M. (March 1988). "Some Asimov Resonances from the Enlightenment". Science Fiction Studies. 15 (1): 36–47. JSTOR 4239857. Retrieved 8 October 2021.
- Edwards, Belen (November 19, 2021). "How Apple TV's 'Foundation' is different from the books". Mashable. Retrieved 2022-02-14.
- "Sample of Foundation's Triumph". Archived from the original on 2007-03-10. Retrieved 2019-06-18.
- Palumbo, Donald E. (2016-04-27). An Asimov Companion: Characters, Places and Terms in the Robot/Empire/Foundation Metaseries. McFarland. ISBN 978-1-4766-2394-8.
- Manlove, Colin N. (1986-06-18). Science Fiction: Ten Explorations. Springer. ISBN 978-1-349-07259-0.
- Myers, Marcia J. (June 1998). "Images of Librarians in Science Fiction and Fantasy: Including an Annotated List". Education Resources Information Center. Institute of Education Sciences. Retrieved 11 October 2021.