Hari Seldon

Using psychohistory, he found the right time and place to set up a new civilization, that would overtake the old Galactic Empire by sheer force of social pressure, in a 1,000 year time span.

The Foundation Trilogy, with the expanded Foundation Series, deals with the first four centuries of this time. Asimov, after writing four books in chronological order, went back with two books to better describe the initial process. While Hari Seldon appeared only as a mythological figure in the original Trilogy, the two last books describe his life in considerable detail.

Asimov managed to merge the Foundation series with his other famous Robot series, using R. Daneel Olivaw as a link.