Hari Seldon is the intellectual hero of Isaac Asimov's Foundation Series. In his capacity as mathematics professor at Streeling University on Trantor, he developed psychohistory, allowing him to predict the future in probabilistic terms.

In the first five books of the Foundation Series, Hari Seldon made only one in-the-flesh appearance, in the first chapter of the first book (Foundation), although he did appear other times as pre-recorded messages. After writing five books in chronological order, Asimov went back with two books to better describe the initial process. The two prequels—Prelude to Foundation and Forward the Foundation— describe his life in considerable detail. He is also the central character of the Second Foundation Trilogy written after Asimov's death (Foundation's Fear by Gregory Benford, Foundation and Chaos by Greg Bear, and Foundation's Triumph by David Brin), which are set between Asimov's two prequels.

Foundation

Hari Seldon (cover art for Foundation, by Stephen Youll)

Using psychohistory, Seldon found the right time and place to set up a new society, one that would replace the collapsing Galactic Empire by sheer force of social pressure, over a thousand-year time span.

Prelude to Foundation

As a thirty-two year old assistant professor of mathematics at Helicon University, Seldon visits Trantor from his native Helicon to attend the Decennial Mathematics Convention. He presents a paper which indicates that one could theoretically predict the Galactic Empire's future. At first, Seldon has no idea how this could be done in practice, and he is fairly confident that no one could actually fulfill the possibility. Shortly after his presentation, he becomes a lightning rod for political forces who want to use psychohistory for their own purposes. The rest of the novel tells of his flight, which lasts for approximately a year and which takes him through the complex and variegated world of Trantor. During his flight to escape the various political factions, he discovers how psychohistory can be made a practical science. It is in this novel that he meets his future wife Dors Venabili, future adopted son Raych Seldon, and future partner Yugo Amaryl.

Forward the Foundation

This novel is actually told as a sequence of short stories, just as was the case with the original trilogy. They take place at intervals a decade or more apart, and tell the story of Hari's life, starting about ten years after Prelude and ending with his death. The stories contrast his increasingly successful professional life with his increasingly unsuccessful personal life.

In his capacity as First Minister, he gains the nickname Raven for his dire predictions of the future.