The End of Eternity by Isaac Asimov is a science fiction novel, with mystery and thriller elements, on the subjects of time travel and social engineering. It was first published in 1955.

The Eternity of the title is an organisation which exists outside time. It is staffed by humans (specifically male humans only) called Eternals who are recruited from different eras of human history starting in the twenty-seventh century. The Eternals have the capability of ranging up and down time and entering the conventional world at any point of their choice. Collectively they form a corps of Platonic guardians who carry out carefully planned actions within the temporal world in order to minimise human suffering as integrated over the whole of human history.

This has the effect of denying humanity's access to the stars, as alien species advance technologically and confine humanity to Earth. The story's protagonist, realizing this, sabotages the initial creation of the Eternals, allowing humanity to explore the stars. The plot provides an example of a Strange loop. The Eternals make use of time travel in an effort to protect humanity while the bulk of humanity has no idea that Eternity exists in order to change Reality. The Eternals never realize that they are themselves causing the biggest catastrophe that ever besets human kind. In order to correct the situation, humans from the distant future must secretly infiltrate and manipulate the Eternals.

This is one of the finest time travel novels, which climbs above the usual genre, and even refers to it in one discussion. The depiction of the 'Kettles', a sort of temporal elevator that the Eternals use to reach the various centuries, and the manner in which the Eternals change Reality using the minimum necessary change is exciting and bears repeated reading. The novel's concept came from the discovery of a drawing which resembled a mushroom cloud - some years before 1945. What if the drawing was actually a message from a time traveller, stuck in the pre-atomic age, attempting to contact his comrades in the distant future, or 'upwhen' as Asimov names it here.

Asimov placed a hint in Foundation's Edge many years later, that the Eternals might have been responsible for the all-human galaxy of the Foundation Series, but that interpretation is disputed.