In the mid-21st century, crop blights and dust storms threaten humanity's survival. Joseph Cooper, a widowed engineer and former NASA pilot, runs a farm with his father-in-law Donald, son Tom, and daughter Murph. Living in a post-truth society, Cooper is reprimanded for telling Murph that the Apollo missions did occur; he encourages her to carefully observe and record what she sees. They discover that strange dust patterns on Murph's bedroom floor, which she first attributes to a ghost, result from gravity variations and translate into geographic coordinates. These lead them to a secret NASA facility headed by Cooper's former supervisor, Professor John Brand, who explains that 48 years earlier a wormhole appeared near Saturn, opening a path to a distant galaxy with twelve potentially habitable planets located near a black hole named "Gargantua". Twelve volunteers had previously traveled through the wormhole to individually evaluate the planets, and astronauts Miller, Edmunds, and Mann reported positive results. Professor Brand explains he has conceived two plans to ensure humanity's survival. Plan A involves developing a gravitational propulsion theory to propel a mass exodus, while Plan B involves launching the Endurance spacecraft with 5,000 frozen human embryos to colonize a habitable planet. Cooper is recruited to pilot the Endurance. When Murph refuses to see him off, he leaves her his wristwatch to compare their relative time when he returns.
The crew consists of Cooper, the robots TARS and CASE, and scientists Dr. Amelia Brand (Professor Brand's daughter), Dr. Romilly, and Dr. Doyle. After traversing the wormhole, Romilly studies the singularity while Cooper, Doyle and Amelia descend in one of four landing crafts to investigate Miller's planet, an ocean world. After landing in knee-high water and finding only wreckage from Miller's ship, a gigantic tidal wave kills Doyle and delays departure. Due to the proximity of the black hole, time is severely dilated. As a result, 23 years have elapsed for Romilly on Endurance by the time Cooper and Brand return. Edmunds' planet has slightly better telemetry, but Mann is still broadcasting from his, so Cooper rules they use their remaining fuel to reach Mann's planet. En route, they receive messages from Murph, now a scientist, who has learned from Professor Brand on his deathbed that Plan B was his only real plan; Plan A required unattainable data from within a black hole to be successful. On Mann's frozen planet, the Endurance crew revive Mann from cryostasis. He assures them colonization is possible, despite an extreme environment. On an excursion, Mann attempts to kill Cooper and reveals that he broadcast falsified data in the hope of being rescued. He steals a lander and heads for the Endurance.
While a booby trap set by Mann kills Romilly, Amelia rescues Cooper with a second lander and they race to the Endurance. Mann is killed in a failed manual docking operation, severely damaging the Endurance. After a difficult docking maneuver, Cooper regains control of Endurance. With insufficient fuel to reach Edmunds' planet, they use a slingshot maneuver so close to Gargantua that time dilation adds another 51 years. In the process, Cooper and TARS jettison themselves to save weight and ensure Endurance can reach Edmunds' planet. Slipping through the event horizon of Gargantua, they eject from their respective landers and find themselves in a tesseract, possibly constructed by humans of the far future. Across time, Cooper can see through the bookcases of Murph's old room on Earth and weakly interact with its gravity. Realizing that he is now Murph's "ghost", he manipulates the second hand of the wristwatch he gave her, transmitting quantum data via Morse code that TARS collected from inside the event horizon. Cooper and TARS are ejected from the tesseract. Cooper awakes on a space habitat orbiting Saturn. He reunites with his daughter, now an old woman nearing death. Using the quantum data, she was able to develop the gravitational propulsion theory from Plan A, enabling humanity's exodus and survival. She reminds Cooper that Amelia is out there alone. Cooper and TARS take a spacecraft to rejoin Amelia and CASE, who are beginning a human colony on Edmunds' habitable planet.
