Foundation series

The Foundation series is a science fiction series by Isaac Asimov. For nearly thirty years, the series was a trilogy: Foundation, Foundation and Empire, Second Foundation. It won the one-time Hugo Award for "Best All-Time Series" in 1966. Asimov began adding to the series in 1981, with two sequels: Foundation's Edge, Foundation and Earth, and two prequels: Prelude to Foundation, Forward the Foundation. The additions made reference to events in Asimov's Robot and Empire series, indicating that they were also set in the same fictional universe.