Innerspace is a 1987 American science fiction comedy film directed by Joe Dante and produced by Michael Finnell, inspired by the 1966 film Fantastic Voyage. The film stars Dennis Quaid, Martin Short, Meg Ryan, Robert Picardo, and Kevin McCarthy.

Innerspace was released in the United States by Warner Bros. The film received positive reviews from critics, grossed an estimated $95 million worldwide, and won an Academy Award for Best Visual Effects, the only film directed by Dante to do so.

In San Francisco, aviator Lt. Tuck Pendleton resigns his commission and volunteers for a secret miniaturization experiment. He is placed in a submersible pod and both are shrunk to microscopic size. They are transferred into a syringe to be injected into a rabbit, but the lab is attacked by a rival organization that plans to seize the experiment and steal the miniaturization technology.

Experiment supervisor Ozzie Wexler escapes with the syringe, and a chase ensues. At a nearby shopping mall, one of the rivals' henchmen, Mr. Igoe, shoots Ozzie. To stop the experiment from falling into the rivals' hands, the wounded Ozzie injects Tuck and the pod into an unsuspecting passerby—Safeway grocery clerk Jack Putter.

Unaware of what has happened, Tuck believes that he has been injected into the rabbit. After attempts to radio the lab are unsuccessful, he navigates to the optic nerve and implants a camera to see what the "host" sees. Realizing that he is inside a human, he makes contact by attaching another device to Jack's inner ear, enabling him to talk to Jack. Before the pod runs out of oxygen, Jack must help extract Tuck by going back to the lab.

At the lab, the scientists explain to Tuck and Jack that the other group stole one of two computer chips that are vital to the process. The second chip is inside Tuck's pod. Their mastermind is Victor Scrimshaw.

Jack contacts Tuck's estranged girlfriend, Lydia Maxwell, a reporter who has had dealings with "the Cowboy," one of Scrimshaw's henchmen. They learn that he plans to buy the computer chip from Scrimshaw and stake out his hotel. After following him to a nightclub, Lydia seduces him. Jack follows Lydia and the Cowboy back to the hotel and knocks the latter unconscious. Tuck then uses the pod's equipment to control Jack's facial muscles, altering his features so he looks like the Cowboy. Lydia and Jack, posing as the Cowboy, meet with Scrimshaw to steal the chip from him. However, as they are about to take possession of it, Jack's nervousness overrides his transformation, exposing the scam. Igoe captures Lydia and him, and takes them to their laboratory. While imprisoned, Jack and Lydia kiss, which, unknown to them, transfers Tuck into Lydia's body through their saliva. Once taken to the laboratory, the criminals shrink Igoe and inject him into Jack to locate Tuck, kill him, and obtain the other chip that is attached to the pod.

Jack and Lydia soon free themselves and order everyone in the laboratory, including Scrimshaw and scientist Dr. Margaret Canker, into the miniaturization device at gunpoint. Not knowing how to operate it, though, they accidentally and unknowingly shrink everyone to half their original size while trying to retrieve the chip. While trying to re-establish contact with Jack, Tuck discovers a growing fetus and realizes that he's inside Lydia's body, and that she is pregnant with his child. By going to her eardrum and playing their song, he manages to alert them of what has happened. Jack and Lydia kiss again to transfer him back. They drive back to the lab to enlarge him, not realizing that the shrunken Scrimshaw and Canker have escaped and are hiding in the back seat. While they attempt to subdue Jack and Lydia, Igoe locates Tuck in Jack's esophagus and attacks him, severely crippling the pod. Tuck disables Igoe's craft, but he ejects and uses a drill to puncture one of Tuck's air tanks and the windshield. Tuck is able to kill Igoe by dropping the pod into Jack's stomach acid and dissolving him after agitating Jack's anxiety to increase the acidity.