The film opens in Tara, a cotton plantation owned by the proud Gerald O'Hara (Thomas Mitchell), a self-made man of Irish descent, in the Confederate state of Georgia near Atlanta. The date is April 1861. He and his wife, Ellen (Barbara O'Neil), have three beautiful daughters; Suellen (Evelyn Keyes), Carreen (Ann Rutherford), and the headstrong 16-year-old Scarlett (Vivien Leigh). Scarlett spends her days having fun, tormenting the household servants, and flirting, especially with twins Brent and Stuart Tarleton (Fred Crane, George Reeves). The brothers anticipate the next ball and hope Scarlett will choose one of them to attend the ball. The Tarletons speculate the impending war between the North and the South due to the recent attack on Fort Sumter. Scarlett finds the latter topic boring and is certain that there will be no war. She runs off to meet her father who is riding home through the fields. He returns home with some news.
Neighbor John Wilkes (Howard C. Hickman) hosts a barbecue party at his Twelve Oaks plantation. Scarlett pines for Wilkes' son, Ashley (Leslie Howard), a lanky, soft-spoken young man of refined bearing, though he doesn't reciprocate her feelings. While she prepares for the party her servant, Mammy (Hattie McDaniel), walks in with a large tray of food meant for Scarlett to eat so she won't eat at the picnic. Scarlett refuses to eat and also insists on wearing her favorite dress with a plunging neckline, hoping to attract attention from the single men (beaux) at the party. Mammy is more willful than Scarlett and finally gets her to comply, though Scarlett wins the fight over what dress she will wear.
At the picnic Scarlett flirts shamelessly with other beaux despite her willful obsession for Ashley. All the young women go inside for an afternoon nap while the men meet in the parlor for cigars and brandy. Most of them boast of how the South will surely win the war but one gentleman, Rhett Butler (Clark Gable), a visitor from Charleston, South Carolina, disagrees. He states that the South cannot win a protracted war purely through the exhibition of pride and notes how the North is better equipped and industrially superior, able to produce weapons of war quickly. Charles Hamilton (Rand Brooks) is offended by Rhett's opinion and openly tells him so, even going so far as to suggest a duel. Rhett, knowing full well that he's a much better shot than Charles and that this argument is not worth his life, leaves. Charles brands Rhett a coward but Ashley assures him that Rhett would have killed him in the duel.
While the other girls are sleeping, Scarlett slips away from the nap room to speak to Ashley in the parlor. She declares her love for him but Ashley tells her that he intends to marry his cousin Melanie Hamilton (Olivia de Havilland), Charles' sister. Scarlett is infuriated and berates Ashley for making her think he was in love with her. She maintains that Melanie is too fair and can't compete with Scarlett's looks, despite the fact that Melanie is admired for her kindness and altruism. Ashley then walks out of the parlor. In her anger, Scarlett throws a vase at the wall, breaking it to pieces. Rhett Butler suddenly pops up from the couch where he'd been resting and jokingly asks whether the war has begun. Scarlett is outraged and defends Ashley when Rhett mocks him. When Scarlett leaves, Rhett laughs to himself: Scarlett has announced that she would hate Ashley forever, but she still defends him.
The start of the war is finally announced and all the young gentlemen rush to enlist. Charles Hamilton is betrothed to Ashley's sister, India (Alicia Rhett) but, when Scarlett flirts with him to get a rise out of Ashley, he proposes to her instead. Still angry at Ashley for rejecting her, Scarlett agrees. They quickly marry before Charles leaves for the front lines. Scarlett offers herself to Ashley but he denies her again, kissing her lightly on the cheek. Just a few months later, news comes of Charles' death from illness while stationed at the front.
Wishing for her widowed daughter to cheer up (though Scarlett is sullen for the wrong reasons), Ellen suggests that she go to Atlanta to live with Melanie and her Aunt Pittypat (Laura Hope Crews). Scarlett agrees to go, but only because it will give her the chance to see Ashley again. Mammy, believes this decision is not in Scarlett's best interest and tells her so.
In 1862, Scarlett attends a fund raising ball for the Confederate Army in Atlanta where she, as a recent widow, is not supposed to enjoy herself and must remain off to the side wearing a black gown. She dances surreptitiously behind the counter of her charity stall, receiving looks of disapproval as the people around her whisper rumors of her supposed mourning. Rhett Butler is also in attendance, now known as an arms smuggler to benefit the Southern cause despite his cynical attitude towards the war's aims. His motivation is simply to make a profit and his skills in smuggling allowed him to obtain the ball decorations and make it past Southern blockades. Melanie, by now having married Ashley, offers her wedding ring as a war contribution, a generous move that Scarlett feels obliged to follow. This incites Rhett to sarcastically praise her consideration. An auction is then held for the men to bid on a dance with a girl of their choosing. Rhett wins the auction and chooses Scarlett, causing consternation in the crowd because of Scarlett's position as a widow. However, she accepts Rhett's invitation to dance and, while they do, Rhett tells her that he someday wants to hear her say that she loves him. Scarlett confidently proclaims that will never happen as long as she lives.
Another year later, Christmas of 1863 arrives and Ashley returns home from the war front on furlough. Still in love with him, Scarlett once again attempts to woo him but with no success. Just before Ashley's departure day, Scarlett manages to see him alone and gives him a present, tearfully confessing that she only married Charles to hurt him. Ashley makes Scarlett promise to take care of Melanie before they share one passionate kiss. Ashley leaves once more to rejoin the war effort.
Eight months pass, during which the war drags on and the situation in the South worsens. Food becomes scarce and nearly every family has lost loved ones to battle. Scarlett and Melanie, now pregnant with Ashley's child, volunteer as nurses caring for wounded soldiers in nearby Atlanta. Scarlett despises her new role, doubled upon her responsibilities as the sole person to manage Aunt Pittypat's home since Pittypat is incompetent and Melanie grows weaker due to her difficult pregnancy. Scarlett faces the harsh realities of war as she listens to a dying soldier (Cliff Edwards) reminisce about his brother Jeff and witnesses another (Eric Linden) suffer a leg amputation without anesthetic. The useless Aunt Pittypat leaves the city, finding the noise of artillery annoying, and renders Scarlett to care for the weakened Melanie with no one but the house servant, Prissy (Butterfly McQueen), to help.
When Melanie goes into labor, Scarlett, intent on keeping her promise to Ashley, employs the help of Dr. Meade (Harry Davenport) who had previously been watching Melanie's progress. However, he is unable to leave the train station where he is tending to hundreds of wounded and dying Confederate soldiers. When Prissy, who had claimed to know all there is to childbirth, admits that she knows nothing, Scarlett takes control, fueled by her anger. Though Melanie's labor is long and complicated, she eventually gives birth to a son (Patrick Curtis) but is left severely weak.
Scarlett sends Prissy to find the one man who can get them all safely out of Atlanta before the approaching Union troops take siege: Rhett Butler. Prissy finds him enjoying himself at a local brothel run by Belle Watling (Ona Munson). Though Rhett mocks Prissy, he agrees to assist Scarlett who insists on returning home to Tara. Rhett steals a horse and cart and fetches Scarlett, Melanie, her baby, and Prissy, taking them through Atlanta as the city burns in wake of the Union advance. They fight off some looters who try to steal their horse. Once safely outside the city, Rhett leaves them to continue to Tara alone, telling Scarlett that he going to enlist in the Confederate army because he believes only in lost causes 'when they are really lost'. Scarlett begs him not to go and he professes his love for her, claiming to have never loved anyone else so fiercely. Scarlett rebuffs his advances but he kisses her, paying for it with a slap across the face. Rhett gives her his pistol and walks off, leaving Scarlett in tears.
The women continue on their journey to Tara alone, traveling mostly by night to avoid enemy Federal troops. When Melanie can no longer lactate for the baby, they resolve to milk a stray cow for sustenance. They pass the Wilkes' plantation which has befallen the same fate as many others, having burned to the ground. Melanie tries to stand but collapses upon seeing the scorched crosses marking the graves of her entire family. Under moonlight and just as their horse dies of exhaustion, they arrive at Tara to find it still standing but derelict, having been used as headquarters for Northern troops. The fields are untended and the grounds have been pillaged but Scarlett finds that her father, her sisters, and two of their house servants, Mammy and Pork (Oscar Polk), remain, the rest of the servants/slaves having either run away or forced into the Union army. Scarlett discovers that her mother recently passed away from typhoid fever, leaving her already disturbed father practically insane. With barely any food, no livestock to speak of, and no money, Scarlett wanders into the fields to clear her head. She pulls a dried up carrot out of the ground to bite into it, only to throw up immediately afterwards. Resolving not to give up, she stands defiantly, saying, "As God is my witness, I'll never be hungry again!"
Months pass and the war enters its final stages. General Sherman marches his Northern armies through Georgia in his so-called 'March to the Sea', leaving destruction in his path. Scarlett and her sisters have been forced to make the best of things, performing manual labor themselves to keep Tara running and in repair. Melanie remains weakened from childbirth and is reduced to staying in bed for the most part. At the moment when Scarlett is scolding her for getting out of bed again, wishing to help, a renegade Union soldier (Paul Hurst) enters the home. He claims that he's simply looking for valuables to move on with but, when he threatens Scarlett, she takes the gun that Rhett gave her and shoots him in the face. The Union soldier falls dead down the staircase. Melanie is a witness, having crawled out of bed with a saber. She promises not to tell the others what happened while Scarlett searches the soldier, finding legitimate cash and other valuables. They dispose of the body and explain to Scarlett's father and sisters that her gun had accidentally discharged. Scarlett uses Melanie's nightgown to wrap the dead soldier's bloody head up and drags the body off, planning to bury it in the orchard.
Some months later, in spring of 1865, the war is finally over. Confederate soldiers amble back home in the wake of General Lee's surrender. One of them, Frank Kennedy (Carroll Nye), arrives at Tara and, having long been in love with Suellen, asks Scarlett's permission to marry her. Tara soon becomes a haven for passing soldiers who are given food and rest, mostly at the behest of Melanie, much to the dismay of Scarlett. One soldier (Phillip Trent) gives Melanie the news that Ashley is still alive but is a prisoner at a Yankee camp. Soon enough another few months later, Ashley arrives at Tara and Melanie rushes to embrace him. Scarlett is urged to do the same but is held back by Mammy; she has no rights to him. To her torment, Ashley stays at Tara with Melanie and his son (Ricky Holt).
During the first year-and-a-half of Reconstruction, high taxes are imposed on the Southern plantations by Northern carpetbaggers, much to Scarlett's dismay. Terrified that she will lose Tara, she seeks comfort from Ashley though Mammy doesn't believe a thing of good will come of it. Scarlett begs Ashley to come away with her to Mexico where they can start anew. He kisses her and admits that he loves her and admires her courage but simply can't leave Melanie and his son behind. Ashley reminds Scarlett that she still has Tara which she should love more than him and thrusts some of its red dirt into her hand. He tells her that the Southern civilization is and its way of life with slavery is gone forever and that he intends to move to New York City with his family to work as a banker. Scarlett throws a tantrum and, when the commotion attracts Melanie's attention, she naively suggest that she and Ashley remain in Tara to help Scarlett. Dejected, Ashley gives in.
Jonas Wilkerson (Victor Jory), former overseer of Tara, now prosperous due to collaboration with the carpetbaggers, offers to buy Tara from Scarlett. Though the tax has risen to nearly $300, Tara rejects the offer and humiliates Jonas by throwing a clump of dirt in his face. As he leaves, Scarlett's father, his mind all but completely lost, chases him down on his horse, attempting to upbraid him. However, the horse falls while attempting to jump over a fence and O'Hara is killed in the fall.
After burying her father, Scarlett seeks the help of the only man she knows of, yet again: Rhett Butler. Despite holding a Captain's rank, Rhett is being held in the city jail in Atlanta by Union forces who are threatening to hang him unless he hands over his Confederate gold. Prior to the war, Rhett had moved all his wealth to banks in London where it would be safe. Conditions in the jail, however, are hardly bleak: Rhett plays cards, gambles and drinks with Union soldiers, tells them stories about his life as a blockade runner, and he even and receives female visitations. Scarlett decides to dress up for the occasion and enlists Mammy to create a new dress for her out of the curtains hanging at Tara. Mammy accompanies Scarlett to Atlanta to keep her out of trouble. Posing as one of Rhett's "sisters", Scarlett is allowed visitation to Rhett at the city jail and attempts to present herself with an air of elegance, claiming that life at Tara is like paradise. Rhett, however, sees through the deception when he notices her roughened hands from working the fields. Despite her anger, she continues to beg for money and even offers to be his mistress. Rhett dismisses her and informs her that if he'd tried to use his own funds to help her, the Union would come down on him immediately. On her way out, Scarlett passes Belle Watling waiting for a visit. Noticing how well-dressed she is, Scarlett figures that she knows how to get the money.
While walking through town, Mammy and Scarlett come across Frank Kennedy, now a successful businessman selling hardware and wood for which the city is being rebuilt. Frank claims to be saving all his money to marry Suellen and bring her to the city. Sensing an opportunity, Scarlett tells Frank that Suellen has married another man and presents herself open to Frank, despite Mammy's disapproving looks. Arriving back at Tara, Suellen is heartbroken and sullen, having just learned that Scarlett hastily married Frank and that he has paid off Tara's debts. She scolds Scarlett for having been married twice already and relents that she seems to be destined as a spinster.
Throughout that year (1866), Frank's hardware and lumber store flourishes under Scarlett's management. She refuses credit to her poor neighbors and makes lucrative deals with Northern businessmen. They expand further, buying a sawmill, and Tara starts to regain part of its former splendor. Scarlett hires hungry convicts who are exploited by a cruel, former prison overseer (John Wray). Ashley expresses his discomfort at the thought of the convicts being abused, starved and used as slave labor but Scarlett is determined to allow it.
One day, Scarlett comes across Rhett Butler, who is now free and very wealthy. He laughs, saying that she could have married him and become rich if she had waited. She brushes him off and leaves alone for the sawmill. Rhett points out that the shantytown on the way to the sawmill is full of dangerous criminals and Army deserters but Scarlett shows him that she carries the gun he gave her.
On the way to the sawmill, two men attack Scarlett from behind and overpower her before she can use her gun. Panicked, Scarlett faints. The men appear to be on the verge of raping her when Big Sam (Everett Brown), a former slave at Tara, saves her by beating up the two men who flee. News of the event spreads quickly through the town. That evening, Frank drops Scarlett and Mammy off at the Wilkes' home while he and Ashley go out to a political meeting. The women sense that something is afoot and Melanie reads aloud from the book 'David Copperfield' in an attempt to relieve the tension. Rhett appears some time later and tells the women that the men have formed a vigilante group to punish the attackers but that the Union army has been tipped off and those at the meeting are now in danger. Melanie tells Rhett where they are meeting, considering him trustworthy despite Scarlett's advice to the contrary. Rhett says he will do what he can.
Several hours later, Rhett appears back at the home with Ashley and Dr. Meade, with a squad of Union soldiers right behind them. The three men seem to be completely drunk and Rhett tells the Yankee captain, Tom (Ward Bond) that they have just spent the evening at the bordello establishment of Belle Watling, who should confirm their story. The women, including Scarlett, are shocked and embarrassed, but the Yankee captain believes the explanation and departs after apologizing for their intrusion, after Rhett reminds Tom he is also a frequenter of Belle's bordello as well. Once the Union troops leave, Rhett drops the curtain and instantly sobers (having just pretended to be drunk), revealing there was a skirmish in the shantytown. Ashley is wounded, having been shot in the shoulder but the two men who attacked Scarlett are now dead, along with several others. More worried about Ashley, Scarlett neglects to inquire about her own husband, Frank. Rhett finally mentions that he was killed in the skirmish and is still there, lying dead in the road.
Some days later, Melanie meets with Belle Watling and thanks her for helping their men stay out of trouble by backing up their false alibi. Belle says that she has a son studying up North and helped the men because of Melanie rather than Scarlett. Belle cautions Melanie about speaking to her in public from now on as it would damage Melanie's reputation but Melanie persists that she would be happy to speak to Belle anytime.
A few days later Rhett visits the now twice-widowed Scarlett. He realizes that she has been drinking heavily despite her attempts to cover up the smell with cologne. She tells Rhett that she will never love him because she's in love with another man, but she will marry him because of his money. Rhett says that they are two of a kind; partners in crime, and he marries her anyway. Rhett and Scarlett have a luxurious honeymoon in New Orleans and return to Tara so that Scarlett can use her new riches to restore its full glory. Rhett also buys a large mansion in Atlanta where they will live on a regular basis. In time they have a child whom Rhett confidently names Bonnie Blue Butler after Melanie remarks (newborn: Kelly Griffin, 2 year-old: Phyllis Douglas) on her brilliant blue eyes.
After her daughter's birth, Scarlett becomes depressed over her waning youth and her unrequited love for Ashley. She informs Rhett that she wants no more children and will no longer sleep with him. Furious, Rhett threatens her with divorce and storms out to find consolation at Belle Watling's. Although he has grounds for divorce, Rhett continues with the sham marriage in order to keep up social appearances for Bonnie's sake. Bonnie becomes a sort of substitute for Scarlett in Rhett's eyes. Over the next few years, Rhett dotes on the child, spoiling her and giving her the best of everything, including a pony and riding lessons.
In 1871, India Wilkes and Mrs. Meade (Leona Roberts) discover Scarlett hugging Ashley at the hardware store. Although the hug was rather innocent, Scarlett knows that rumors will fly. That night is Ashley's birthday party and Rhett, who has heard the gossip, forces Scarlett to go in a daring red taffeta dress which would be considered very inappropriate for the occasion. Melanie is the only person who welcomes Scarlett. Back at the Atlanta mansion, Scarlett finds Rhett completely drunk. They have an angry confrontation and, this time, Rhett refuses to take no for an answer. He carries Scarlett off to the bedroom. The next morning, Scarlett seems deliriously happy. When Rhett arrives to apologize and propose a divorce, her good mood vanishes. Rhett promises to take care of Scarlett financially but insists on taking Bonnie away with him. Scarlett rejects his offer, as it would be a disgrace. Rhett then leaves on an extended trip to London and takes Bonnie with him.
In London some months later, five-year-old Bonnie (Cammie King Conlon) has nightmares and can't sleep in the dark. Her stuffy English nurse (Lillian Kemble-Cooper) believes that the ordeal will build the child's character but Rhett dismisses her and lets Bonnie sleep with a candlelight on. The homesick Bonnie begs to return to her mother. When Rhett and Bonnie return to Atlanta, Scarlett tells him that she's pregnant again. Rhett reacts coldly and Scarlett ups the ante by saying she wishes the baby were not his, to which Rhett retorts, "Maybe you'll have an accident." In the ensuing row at the top of the stairs, Scarlett takes a blind swing at Rhett who dodges it. The momentum causes Scarlett to fall down the stairs and lose her baby.
Later, at the behest of Melanie who has become pregnant again, Rhett makes an effort to be kind to Scarlett. Sitting on the back terrace of their Atlanta mansion, Rhett and Scarlett discuss the possibility of Scarlett giving up the lumber business to devote herself to her husband and child. A reconciliation begins to seem possible when, at that moment, Bonnie insists stubbornly on jumping a fence with her pony after she raised the bar. Scarlett remembers her father's death and has a premonition of disaster. Her worst fears come true as the pony refuses to jump and fatally throws Bonnie over the fence. Rhett is devastated by Bonnie's death and refuses to release the child's body for burial for several days despite Scarlett's wishes. Rhett locks himself in his room with the body after shooting the pony, refusing to allow anyone in, including Scarlett who can only bang on the door screaming at him.
Melanie arrives at the mansion and is led upstairs by Mammy, who tearfully relays the past few days events. Melanie manages to allow Rhett to come out of the room and allow undertakers to take away Bonnie's dead body. But Melanie, overwrought with emotion, collapses and goes into labor. Upon a doctor's examination following the birth, he determines that Melanie is dying from internal bleeding. In a final meeting with Scarlett, Melanie asks her to look after Ashley. When Melanie dies, Ashley is left a broken man and he tells Scarlett that Melanie was always his true love, a devastating revelation to Scarlett, who then realizes that he never really loved Ashley and can only wish that he had been clearer about his own feelings for her. Rhett, witness to the scene, stalks off to his and Scarlett's home.
Scarlett returns to the mansion seeking Rhett. Having seen Scarlett with Ashley at Melanie's house, Rhett tells her that she will never stop loving Ashley and so he is leaving her, for good, to start a new life back in his hometown of Charleston. As Rhett begins to pack his suitcase to leave, Scarlett insists that she now realizes that she loves Rhett and never truly loved Ashley but Rhett maintains that any chance of saving their marriage died with their daughter Bonnie, and on top of all that, he's tolerated Scarlett's drama long enough. As he prepares to walk out the door, Scarlett begs him one last time, asking what will happen to her if he leaves. Indifferent, Rhett replies, "Frankly, my dear, I don't give a damn." and strides out of the house into the evening fog.
Scarlett collapses on the stairs in anguish. She pulls back from despair only when she thinks of the other great love of her life, Tara, through a series of reminiscences in voice-over . Scarlett is determined to return to Tara, make a new start, and try to somehow get Rhett back, saying to herself, "After all, tomorrow is another day!"
In the final shot, we see Scarlett silhouetted against Tara as the sun sets over the hill, having arrived back at her childhood home and now facing an unknown, but new, future.