The movie opens with a news report advertising the way of life in this future, which seems to be far from ideal. Among other stories, three police officers have been murdered and a fourth, Frank Frederickson, has been left critically injured in an attack by unofficial Old Detroit crime boss Clarence Boddicker (Kurtwood Smith), wanted for the deaths of over 30 police officers. The Detroit Metropolitan Police Department's union representatives blame Omni Consumer Products (OCP), who have recently entered a contract with the city to run and manage the DPD, for putting their men in such dangerous environments.
At the Metro West Precinct in Old Detroit, officers respond to a variety of cases when veteran officer Alex Murphy (Peter Weller) arrives, having been transferred in from Metro South. Desk Sergeant Warren Reed gets Murphy a set of riot armor and introduces Murphy to the other cops, who are not happy about how OCP seems to be trying to run the police force into the ground. As Murphy and the other cops are suiting up in the locker rooms, one of them suggests that they go on strike to pressure OCP into giving them better working conditions. At that point, Reed and another officer come in, carrying an evidence tray. Reed removes Frederickson's nameplate from his locker, announcing that Frederickson has died, much to the disappointment of the other cops in the locker room. Reed tells them that a memorial service will be held the next day and admonishes them harshly about striking.
Murphy is brought upstairs where he sees a criminal assaulting his arresting officers. The female officer involved quickly beats the suspected criminal into submission. The tough cop is a woman, Anne Lewis (played by Nancy Allen), a hardened veteran of Metro West. Reed decides that she will be partnered with Murphy. They leave to go on patrol; Murphy insists that he drive the car.
The action changes to OCP Headquarters, where executives Donald Johnson (Felton Perry) and Bob Morton (Miguel Ferrer) are on their way to a board of directors meeting. They converse on the elevator ride up about what the meeting could be about. Johnson figures that the Old Man is greenlighting the Delta City project, despite Morton pointing out that OCP never does anything ahead of schedule. Morton thinks that Dick Jones is planning to show off his new droid, the ED-209 series.
The Old Man (Daniel O'Herlihy) starts the meeting off by reminding everyone that he has had a vision for over a decade, of demolishing "Old Detroit" and redevelop it as a high-end utopia called "Delta City." There's a problem with Old Detroit: it's riddled with crime, and this crime must be eradicated before they can build Delta City. To that end, OCP President Richard "Dick" Jones (Ronny Cox) has funded the development of a new type of law enforcement robot: the Enforcement Droid Series 209, ED-209 for short.
To demonstrate the droid's effectiveness, Jones asks a younger executive, Kinney, to volunteer as a test subject to simulate a typical arrest and disarming procedure. Kinney is handed a Desert Eagle pistol, and Jones instructs him to use it in a threatening manner. Kinney aims the pistol at ED-209. When he cocks it, ED-209 immediately turns on and aims its machine guns at Kinney, ordering him to drop his gun in the next 20 seconds. Kinney immediately tosses the pistol away, but ED-209 suddenly steps forward, growls and tells Kinney he now has 15 seconds to comply. The board goes into chaos and the scientists frantically try to shut ED-209 off as Kinney tries to hide among his fellow executives, who push him back into the line of fire. When ED-209 reaches zero, he declares that he is authorized to use physical force and opens fire, throwing Kinney onto the model of Delta City and riddling him with bullets. He continues to shoot Kinney for fifteen seconds, only stopping once the engineers are able to unplug him.
The Old Man is not happy with the outcome of Jones's product, citing the expense involved in designing the droid and the potential for lost interest payments, even though Jones insists that this is "just a glitch." Morton takes advantage of the opportunity to tell the Old Man about his own project. He and the people at Security Concepts have been working on a backup plan in the event that ED-209 would not function properly, known as "RoboCop." Morton also states that he hopes to have the first RoboCop in prototype within 90 days, and he's had the police force restructured so that the best candidates for the project are in the highest risk areas. The Old Man is impressed by Morton's idea and decides to put his project up as priority. Jones, however, is not pleased at being upstaged.
Meanwhile, Lewis and Murphy are out on patrol and stopping for coffee. Murphy is relaxing by spinning his pistol on his fingers, which he explains to Lewis a move he learned from a television show that his young son watches. He thinks that all good cops like him need to be role models to their kids. They are interrupted by a radio call about a pharmaceutical company being robbed by a group of men driving a silver panel truck. Murphy and Lewis jump into their car and drive off to track them down.
In the back of said panel truck are Clarence Boddicker and his gang - Bobby, Leon Nash (Ray Wise), Joe Cox (Jesse D. Goins), Steve Minh (Calvin Jung), and getaway driver Emil Antonowsky (Paul McCrane), who have just successfully robbed a pharmaceutical company and emptied the store's safe of money. Boddicker is furious to find that Bobby had burned all the money when blowing the vault's door open, rendering it obviously too easily identifiable to pass and thus useless. He goes off on a tirade on Bobby, slapping him several times, but is interrupted when Emil looks in his reviewer mirror and yells that there's a cop chasing them. Leon rushes over to the back doors, looks out the window, and sees Murphy and Lewis following them. Boddicker orders Emil to slow down so they can ambush their pursuers. Emil thinks Boddicker is crazy, but reluctantly obeys, as Boddicker and the other gang members begin loading their shotguns.
In the police car, Murphy radios for help, but to his and Lewis' dismay, there is no backup available to assist them. He draws his pistol and Lewis' sidearm as well and they speed up, hoping to take the panel truck by surprise.
On Boddicker's signal, Bobby kicks open the back doors and the gang members open fire...on empty air. They wonder where the unit has gone, until Emil looks out the passenger window and sees Murphy and Lewis driving alongside them. Boddicker rushes to the passenger window, shotgun in hand and fires at Murphy, who fires back with both pistols. Lewis drops back behind the truck, and Murphy opens fire again. Suddenly, Bobby falls, two bullets in his right leg. The other gang members continue shooting, and riddle the car with bullets. Boddicker decides that Bobby is no longer useful to him. The other gang members grab him and Boddicker asks, "Can you fly, Bobby?" Bobby pleads for his life, only for the other gang members to throw him onto the police car, crushing the windshield. Lewis, startled, spins the car out while Boddicker and his gang drive away, cackling manically. Lewis and Murphy back up, rolling Bobby off the car, and then drive off in pursuit.
Murphy and Lewis track the truck down to an abandoned steel mill. They become separated as they split up to search for Boddicker and his men. Lewis stumbles on Cox as he is relieving himself. He attacks her and pushes her from a catwalk, knocking her unconscious.
Murphy finds Emil and another thug, Dougy, watching the terrible sitcom It's Not My Problem on a TV set. Surprised by Murphy's appearance, Dougy tries to grab a shotgun, but is shot dead by Murphy. He forces Emil to surrender, saying "dead or alive, you're coming with me". But as Murphy is about to put his handcuffs on Emil, Steve Minh and Leon Nash appear with shotguns in hand and train them at his head. As the two advance on Murphy, Emil disarms Murphy, then grabs his own shotgun, pumps it, and declares, "Your ass is mine!"
At that point, Boddicker himself shows up, and knocks Murphy to the ground with the butt of his shotgun, demanding to know where Murphy's partner is. Cox enters the room and jokingly talks about taking out Lewis. Boddicker puts his hand on the side of Murphy's neck and asks the cop what he thinks of him. Murphy replies, "Buddy, I think you're slime." The other gang members laugh, and Boddicker admits that there's one problem: cops do not like him, and he does not like cops.
Boddicker throws Murphy to the floor and aims his shotgun as he moves it across Murphy's body while miming the sound of a tracker, until he shoots off Murphy's right hand. Murphy tries to stifle the bleeding with his left hand as he stands up and tries to stagger away. Emil then takes his turn and fires, the bullet ripping off Murphy's right arm at the shoulder. Murphy screams in agony as Emil, Leon, Cox, and Minh proceed to empty their shotguns into Murphy, riddling his torso with bullets. Lewis is a witness to the massacre, though she doesn't see Murphy getting hit, but from behind a chain link fence, she can see the gang shooting firing-squad style. Amazingly, when the gangs' shotguns run out of ammo, Murphy is still alive. Boddicker casually lights a cigarette, then pulls a pistol and shoots Murphy in the face. Murphy falls to the floor, while Boddicker and his men depart. Once Boddicker leaves, Lewis finds Murphy's mutilated body. Murphy is rushed to a nearby hospital but dies after a valiant effort by the ER team and he's declared dead.
The next few scenes are seen from an unknown perspective as Bob Morton and his staff take Murphy's body and turn it into RoboCop. Morton coldly orders his team to amputate Murphy's left arm. They also inform him that they'll blank his memory. Johnson also mentions that Murphy had signed release forms when joining the force and that they can do what they want with him. RoboCop is built with a unique set of schematics and state-of-the-art equipment including titanium and Kevlar-laminated armor and mechanical hands that can exert 400 ft/lbs of force. Morton is very pleased with the work being done.
Several months later, Morton unveils RoboCop to his fellow OCP executives. A large convoy of scientists and engineers transport him to Murphy's old precinct. At the station, Reed is dealing with a repeat offender at the desk when a large team of scientists and men and women in lab coats start wheeling equipment in through the front door. Reed is about to protest to Morton and his assistant when he is interrupted by odd-sounding footsteps. Behind a pane of frosted glass, we see RoboCop striding in. The other officers eagerly run through the halls to see what is going on as RoboCop is led to his charging station and command center in the holding cells.
At the command center, RoboCop is told to sit in a large diagnostic chair when he is at rest. The engineers tell Morton that RoboCop is fed a rudimentary paste to sustain his organic systems. Johnson tries the paste out and finds that it tastes like baby food. A quick test of his tracking system and a voice stress analyzer to test his ability to record and play back are performed. Morton then asks RoboCop what his three "prime directives" are. 1. Serve the Public Trust, 2. Protect the Innocent, and 3. Uphold the Law. Possibly unknown to Morton and most of his staff, a fourth directive has also been uploaded but is not revealed, listed only as "Classified".
Lewis and some other officers are next seen on the shooting range, but everyone's attention is distracted when RoboCop shows up and begins shooting his own custom pistol, as part of a test of his sharpshooting skills. RoboCop is a straight shooter, successfully using his gun to obliterate several cardboard targets. After the demonstration is complete, RoboCop puts his gun away, and we notice that he twirls it around his fingers on his right hand before storing it in a leg holster built into his right leg, a feature that Lewis finds familiar. Morton tells Reed that RoboCop needs a car. Reed grabs a set of car keys from his desk and tosses them. RoboCop snatches them out of the air and departs. Morton watches him, saying, "Go get 'em, boy!"
RoboCop's first night is quite active. It starts at a mom-and-pop convenience store, when a robber wearing a trench coat enters, and buys a magazine. As he is paying for it, he asks the owners to empty their cash register and safe. When they ask what he is talking about, he whips out a submachine gun and orders them to give him their money. The robber trains his weapon on the husband and orders him to open the safe. The husband insists they don't have a safe and the robber, furious, kicks aside a pile of beer cans to reveal the safe, and threatens to shoot the wife. As he is counting to three, RoboCop suddenly walks in and orders him to drop his weapon. The robber fires at RoboCop, but his bullets only bounce off the machine's bulletproof casing. He continues shooting until RoboCop bends the barrel of his rifle. The robber tries to run, and RoboCop delivers him a blow and throws him into a refrigerator. He very politely thanks the store owners for their cooperation and leaves while they stare in disbelief.
RoboCop is later driving when he receives a report of a molestation in progress. Two lowlifes are chasing down a blonde woman and attempting to cut her hair and rape her. One of them is about to cut her skirt open when a police car screeches to a stop. RoboCop emerges and orders them to let her go. One of the two men grabs the woman and threatens to slit her throat. RoboCop draws his pistol, tracks the thug holding the woman and fires a shot so precise that the bullet goes through the woman's skirt between her legs and hits the thug in his testicles. While the hostage taker collapses, screaming in pain, the grateful woman rushes up to RoboCop and hugs him gratefully, and he offers to call a rape crisis center in his usual monotone that puts her off.
Later still that night, disgruntled ex-city councilman Ron Miller enters City Hall with a submachine gun and takes the mayor and his staff hostage, and kills an aide who refuses to cooperate. The police and SWAT team arrive and set up a perimeter. Reporters gathered at the scene are interviewing Lt. Hedgecock, the hostage negotiator, but are distracted when another police car arrives, breaks through the crime tape and comes to a stop. RoboCop climbs out and is swarmed by the media. The police work to get the reporters out of the way, and RoboCop tells Hedgecock to stall Miller, while he himself goes inside and starts making his way to the second floor.
Hedgecock gets on the mike and offers to hear out Miller's demands. Miller demands to have his old job back. He also demands a bigger office and a new car on the city's bill, specifically a car that has "reclining leather seats, goes really fast and gets really shitty gas mileage." Hedgecock offers the 6000 SUX, but eventually Miller loses his patience. He grabs the mayor and pushes him to the window. As Miller prepares to execute the mayor, RoboCop punches through the wall, grabs Miller and pulls him backwards, his submachine gun firing wildly into the air. RoboCop then spins Miller around and punches him out a glass window, and he falls to the street.
Bob Morton is thrilled by the success of his product, and the fame that RoboCop brings him. However, Dick Jones is still very angry about Morton's upstaging him, and vows revenge. He also warns Bob that his creation's service record had better be spotless.
Some nights later, RoboCop is at rest when he begins having seizures as memories begin to flow through his head, which we realize are the last things Murphy ever saw: it begins with a flashback shot of Clarence Boddicker shooting him in his hand. RoboCop then writhes as he imagines Boddicker's gang emptying their shotguns into him, which causes the reading on a graph to go off the charts. Things get to a head when in his dreams, he sees Boddicker pull a pistol and shoot him in the face. RoboCop stands up and leaves to find these men when he is confronted by Lewis, who asks him his name. RoboCop has no reaction to Lewis, until she refers to him as "Murphy" and he backs off. As the cyborg officer leaves the precinct, one of the doctors assigned to RoboCop calls Morton, who shows up and reprimands both Lewis and Reed for interfering with his project.
In a different part of town, Emil arrives at a gas station on a motorcycle with a submachine gun and robs the on-duty attendant. Emil then waits as his gas is pumped into his bike, asking the attendant what he's reading -- the guy holds up a book on plane geometry. Feeling antagonistic, Emil begins to threaten the attending and is about ready to shoot him when RoboCop shows up, pistol in hand. RoboCop steps towards Emil, saying "Dead or alive, you're coming with me!" Hearing those words, Emil immediately realizes that he's dealing with Murphy, the very man he and the rest of Boddicker's gang murdered at the steel mill. Incredulous, he screams, "We killed you!!" panics, and tries shooting at RoboCop, to no avail. RoboCop pauses, recalling where he remembers Emil from. Emil then uses the leaking gas pump and lit cigarette to blow up the gas station. As he flees, his motorcycle is shot out from under him by RoboCop. He demands that Emil identify himself but the thug is too injured to answer. RoboCop takes Emil into custody and uses a data spike built into his right hand to access the police mainframe and look up Emil's data and known associates. One of the names on the list is Boddicker's name. His rap sheet includes charges for the murder of Officer Alex J. Murphy.
RoboCop goes to Murphy's last known address and finds the house up for sale. Walking through it triggers more memories of Murphy's wife and son, until he snaps. Noticing a monitor showing an advertisement for the new model homes, RoboCop's rage culminates in him punching a fist through the screen. RoboCop tracks down Leon at a night club rave and arrests him, demanding to know where Boddicker is.
Meanwhile, Bob Morton is cavorting with two high-priced hookers in his house. It is going well until the doorbell rings. Morton goes to answer the door, thinking it's someone delivering champagne, but is shocked when he opens the door and Clarence Boddicker himself enters, carrying a suppressed pistol. While holding Morton at gunpoint, he orders "Bitches, leave!" and the two hookers hastily depart. Once they are out, Boddicker shoots Morton in the legs several times, leaving them unable to stand. While Morton gasps in pain, Boddicker then takes out a CD and plays a video message for Morton from Dick Jones. Jones tells Morton that he refused to follow OCP protocol and became too ambitious in pushing past Dick's authority, and he's cashing Morton out of the equation. Boddicker primes a hand grenade, pulls the pin with his teeth, and puts it on the coffee table, just out of Morton's reach and leaves. When the timer hits zero, the grenade detonates and blows up Morton and his house.
Clarence is at a meeting with a competitor at a competitor's cocaine processing factory, trying to work out a distribution deal with his competitor, Sal. Sal is unimpressed with Clarence and his thugs, telling him that his record of killing cops makes him too dangerous to work with. Clarence tells Sal that he can increase his distribution network -- the discussion ends with guns drawn when Clarence insults Sal. Just then, the door to the factory is broken down and RoboCop walks in, ordering everyone to surrender. They open fire and RoboCop kills most of the gangsters and finds Clarence. He brutally beats Clarence, tossing him through several plate-glass windows, then threatens to break the crime lord's neck. Clarence, his swagger gone, weasels out and begs for his life, revealing his connection to Dick Jones. RoboCop realizes that he is a police officer and cannot simply kill Clarence out of revenge.
Back at the police station, the officers have voted to go on strike (a result of OCP cutting back their salaries and pension plan, along with having lost 5 officers in the past week). RoboCop brings in Clarence Boddicker and orders him to be booked on charges of murdering police officers. Dick Jones arranges for Clarence to be freed on bail.
RoboCop goes immediately to Dick Jones' office. As he marches in, he plays a video recording of Clarence's admission of his connection with Jones. RoboCop charges Jones with aiding and abetting and attempts to arrest him, but his systems immediately begin to shut down due to a "Product violation." Jones explains that Directive 4 was created by himself to prevent OCPs "product" from taking action against an OCP Official.
Jones activates ED-209 to destroy RoboCop and admits that he had Bob Morton killed. RoboCop is damaged, but manages to escape by running down a flight of stairs (which works because ED-209's massive feet render him unable to climb or descend stairs without falling -- the robot throws a temper tantrum while RoboCop escapes). Several officers attempt to stop RoboCop for his reported "attack" on Jones, opening fire and damaging him further, when Lewis arrives and rescues him. Lewis and RoboCop retreat to a hidden factory. RoboCop repairs most of the damage to his robot body and removes his helmet, revealing the face of Murphy. Murphy asks what happened to his wife and son; Lewis responds that they moved away after Murphy's funeral to start a new life. Lewis tries to comfort him but he asks to be left alone.
Released from jail, Clarence meets with Jones, whom chastises Clarence for involving him, saying that RoboCop's recorded video of Clarence's admission is admissible in court. Dick orders Clarence to destroy the cyborg; Clarence refuses at first, however, Dick is able to change Clarence's attitude by offering the crime lord free reign during the construction of "Delta City" a planned community that will replace the crime-ridden streets of Detroit, a concept conceived and championed by The Old Man. Clarence will be permitted to extend his influences in drugs, prostitution and gambling to the workers of Delta City, an offer that Clarence knows is too good to pass upon. Dick agrees to provide Clarence with military-level weapons and gives him a tracking device to find their common enemy.
Clarence rallies his gang of thugs to go out and kill RoboCop. Jones had given them large .50-caliber rifles to destroy their nemesis. The crew tracks RoboCop and his partner to the abandoned steel mill where they're hiding. One by one, they are defeated and killed by Lewis and RoboCop -- Joe Cox is killed almost immediately when Murphy targets and shoots him; Emil drives his truck into a giant tank filled with toxic waste that melts his flesh (he is later killed when Clarence collides with him while driving his car). Lewis, involved in a car chase with Clarence, is injured when the villain shoots her several times. Murphy becomes pinned down by scrap metal dropped on him by Leon (who is later killed by Lewis), and is immediately attacked by Clarence, who wields a large rail bar. Murphy is able to fend off Clarence's attacks and stabs Clarence in the neck with his data spike, killing the crime lord.
RoboCop returns to OCP and, using the giant rifle taken from Clarence's gang, destroys the ED-209 Jones has guarding the entrance to their headquarters. RoboCop interrupts a meeting of the OCP board and openly accuses Dick Jones of murder and states that his programming will not allow him to arrest any executive of OCP. Over Jones' protests that the cyborg is psychopathic, Murphy uses his data spike to play the video of Jones' admitting to Morton's murder, which Murphy had recorded just as Jones activated ED-209 in his office.
Jones grabs a gun and takes The Old Man hostage, demanding a helicopter to safely evacuate. The Old Man angrily fires Jones, voiding Directive Four and allowing RoboCop to take action. RoboCop shoots Dick Jones several times, who falls out a window, screaming as he speeds toward the pavement below. The Old Man thanks the cyborg for his actions, asking what the cyborg's name is. RoboCop pauses for a second before responding: "Murphy."