Second Foundation by Isaac Asimov

Second Foundation is the third novel published of the Foundation series by Isaac Asimov, and the fifth in the in-universe chronology. It was first published in 1953 by Gnome Press. The term also describes the organization by that name which is the focus of the book. The organization's existence (and nothing more) had been revealed in Foundation, searched for in Foundation and Empire, and makes brief appearances in this novel. It would not be described in detail until Foundation's Edge.