Do Androids Dream of Electric Sheep? (retrospectively titled Blade Runner: Do Androids Dream of Electric Sheep? in some later printings) is a 1968 dystopian science fiction novel by American writer Philip K. Dick. It is set in a post-apocalyptic San Francisco, where Earth's life has been greatly damaged by a nuclear global war. The main plot follows Rick Deckard, a bounty hunter who has to "retire" (a euphemism for kill) six escaped Nexus-6 model androids, while a secondary plot follows John Isidore, a man of sub-par IQ who aids the fugitive androids.

The book served as the basis for the 1982 film Blade Runner and, even though some aspects of the novel were changed, many elements and themes from it were used in the film's 2017 sequel Blade Runner 2049.

In 1992, after a global war has rendered Earth's atmosphere highly radioactive, most animal species are now endangered or extinct. As a result, owning real animals has become a fashionable and expensive status symbol, while poor people can only afford realistic electric robotic imitations of animals. Also, due to the radiation, people are encouraged to move to off-world colonies with the incentive of free androids: robot servants so similar in appearance to humans that only an empathy test can confirm their identities.

Rick Deckard, a bounty hunter for the San Francisco Police Department, is assigned to "retire" (kill) six defiant and violent androids of the new Nexus-6 model which have recently escaped from Mars and traveled to Earth. Deckard hopes this mission will earn him enough money to buy a live animal to replace his lone electric sheep, which would comfort his depressed wife, Iran. First, Deckard visits the Seattle headquarters of the Rosen Association, which makes the androids, to confirm the accuracy of the empathy test on the new model. For business reasons, Rosen wishes to discredit the test and nearly succeeds. However, the test confirms twice that Rachael Rosen, his host in Seattle, is a Nexus-6 android, which she ultimately admits. Deckard returns to San Francisco to begin his hunt for the group of rebel androids.

Deckard meets and kills a Soviet police contact who turns out to be one of the Nexus-6 renegades in disguise. He then moves to kill his next target, an android living as an opera singer. Meeting her backstage, Deckard attempts to administer the test, but she calls the police, who arrest Deckard and detain him at a police station staffed with officers he is surprised to have never met. An official named Garland accuses Deckard himself of being an android with implanted memories. After a test conclusively proves that Deckard's work is legitimate, Garland draws a gun on Deckard and reveals that the entire station is a sham, claiming that both Deckard and Phil Resch, the station's resident bounty hunter, are also androids. Resch, unaware of Garland's revelation, shoots Garland in the head, escaping with Deckard back to the opera singer, whom Resch next murders in cold blood. Desperate to know the truth, Resch asks Deckard to administer the empathy test on him. The test indicates Resch has sociopathic tendencies but confirms he is human. Deckard then tests himself, confirming that he is also human but has a sense of empathy for certain androids.

Having killed three androids in a day, Deckard is now able to buy his wife Iran an authentic Nubian goat. His next target is an abandoned apartment building where the three remaining android fugitives are assumed to be hiding. Deckard suddenly experiences hallucinations of a man named Mercer, the main martyr-like character in a popular religious movement who is depicted as being continuously assailed by falling rocks. The vision of Mercer tells Deckard to proceed, despite the immorality of the mission. Deckard calls on Rachael Rosen since her knowledge of android psychology may aid his investigation. Rachael declines to help, but reluctantly agrees to meet Deckard at a hotel in exchange for him abandoning the case. At the hotel, she reveals that one of the fugitive androids is the same model as her, meaning that he will have to kill an android that looks like her. Despite having initial doubts about Rachael, Deckard has sex with her, after which they confess their love for one another. Rachael reveals she has slept with many bounty hunters, having been programmed to do so in order to dissuade them from their missions. Deckard threatens to kill her but ultimately holds back and leaves for the abandoned apartment building.

The three remaining android fugitives plan to outwit Deckard. The building's only other inhabitant, John R. Isidore, a radioactively damaged and intellectually below-average human, attempts to befriend them. He is shocked when they callously torture and mutilate a rare spider he discovers. Deckard enters the building, experiencing strange, supernatural vision again, notifying him of an ambush. When the androids attack him first, Deckard is legally justified to kill all three without testing them beforehand. Isidore is devastated and Deckard is rewarded for a record number of Nexus-6 kills in a day. Returning home, Deckard finds Iran grieving because, while he was away, Rachael stopped by their apartment and killed their goat.

Deckard travels to an uninhabited, obliterated region near the border with Oregon to reflect. He climbs a hill and is hit by falling rocks, realizing this is an experience eerily similar to the plight of the prophet Mercer. He stumbles upon a toad (an animal thought to be extinct) but, when he returns home with it, he is crestfallen when Iran discovers it is merely a robot. As he goes to sleep, she prepares to care for the electric toad anyway.