Ella (Eloise Webb) lives with her wealthy parents on a beautiful estate in a peaceful kingdom. From a young age, she is taught by her mother (Hayley Atwell) to believe in the existence of magic, allowing her to befriend many animals on the estate, particularly the mice. Everything is perfect until her mother contracts an illness and dies. On her deathbed, she makes Ella promise that she will always have courage and show kindness to others. Fourteen years later, when Ella (Lily James) is a teenager, her father (Ben Chaplin) marries Lady Tremaine (Cate Blanchett), the widow of an old acquaintance, who has two daughters of her own, Drisella (Sophie McShera) and Anastasia (Holliday Grainger). Ella welcomes her stepfamily warmly, despite the stepsisters' unpleasant attitudes and her needing to protect her mouse friends from her stepmother's cat, Lucifer.
Soon after, Ella's father goes abroad on business, promising his stepdaughters gifts of luxury. His own daughter merely asks for the first branch that brushes against his shoulder on the way. Sadly, he becomes ill and also dies. This new loss results in Lady Tremaine revealing her true cold, cruel, and jealous nature. Taking advantage of Ella's hospitality, she persuades her to give up her room for Drisella and Anastasia, presumably temporarily, while Ella retires to the attic with only her mouse friends to keep her company. Not long after her father's death, Lady Tremaine dismisses the servants, leaving only Ella to do their work. Relegated to nothing more than a servant, she is subjected to cruel mistreatment by her stepmother and stepsisters. She is forbidden to eat with them, and spitefully renamed "Cinderella" after waking covered with soot from the fireplace.
Crushed by their cruelty, Ella goes for a ride into the woods, where she encounters a hunting party. She meets one of the hunters (Richard Madden), who claims to be an apprentice named Kit who lives in the palace. Unknown to her, he is actually the only son of the land's dying king (Derek Jacobi). Despite never learning her name, Kit (a nickname given to him by his father) is enchanted by Ella's charm, kindness, and unique outlook on life and becomes infatuated with her. Upon learning that he has little time left, the King insists that Kit finds a bride at an upcoming ball. Despite the law saying that he must marry a princess, Kit can't get over the mystery girl, and deals with his father into letting every eligible maiden in the land attend.
When the ball is announced, the Tremaine family is ecstatic at the prospect of marrying into royalty. However, when Lady Tremaine refuses to buy Ella a new dress, Ella fixes up an old dress of her mother's with help from the mice. On the night of the ball, Ella tries to join her stepfamily on the way out. But Lady Tremaine, claiming that her mere presence will disgrace them, leads her daughters into ripping up the dress before leaving without her. This seemingly breaks Ella's spirit, and she runs into the garden in tears. She encounters an old beggar woman, who reveals herself to be her Fairy Godmother (Helena Bonham Carter). She subsequently turns a pumpkin into a magnificent carriage, four mice into horses, two lizards into footmen, and a goose into a coachman. She then transforms Ella's dress into a gorgeous blue gown, complete with a delicate pair of glass slippers before sending her on her way with the warning that the spell only lasts until midnight.
At the ball, the entire court is entranced by Ella, especially Kit. She wins the coveted first dance with him, whose true identity she's pleasantly surprised to learn. This irritates the Grand Duke (Stellan Skarsgård), who secretly promised Kit to a princess — a fact that Lady Tremaine overhears. After dancing, Ella and Kit tour the palace and grounds together, slowly falling in love. But before he can learn her name, the clock strikes 11:59, forcing her to flee and accidentally dropping one of her glass slippers at the palace stairs in the process. She manages to get away before the stroke of midnight and hides the other slipper in her room as a memento.
Soon after, the King dies, but not before giving his son permission to find his true love. Once it's announced that every maiden in the kingdom is to try on the slipper, Ella excitedly goes to her room to get the other slipper, only to find her stepmother waiting for her with it in her hand. Lady Tremaine, having figured out her identity from her attitude after the ball, demands that Ella make her the head of the royal household once she becomes queen. She also demands that Ella ensure Drisella and Anastasia get proper husbands as well. Ella refuses, admitting that she regrets not protecting her father, but that she would protect the Prince no matter what becomes of her, Lady Tremaine smashes the slipper against the wall and locks her in the attic. She then brings the shattered shoe and the identity of the mystery girl to the Grand Duke, and strikes a deal with him in exchange, which would reward her with title of a countess and worthy husbands for her daughters. The Duke takes the shattered shoe to Kit, hoping to convince him to forget the mystery girl, but this makes him even more determined than ever to find his true love.
The Grand Duke and the captain of the guards (Nonso Anozie) lead a garrison to try the remaining slipper on all the maidens in the land, all of whom are rejected by its magic, before arriving at the Tremaine estate. When the slipper rejects both stepsisters, they turn to leave, only to hear Ella singing ("Lavender's Blue"), thanks to the mice opening her attic window. The Grand Duke tries to leave anyway, but one of the men reveals himself to be Kit in disguise, and demands that the captain investigate the sound. Once Ella is found, Lady Tremaine tries to forbid her from trying on the shoe, but is overruled by the Captain, who defends her. Ella curtly tells Lady Tremaine that she is not and never will be her mother before leaving the attic. She and Kit are finally reunited. Sure enough, the slipper fits perfectly and the stepsisters both plead for forgiveness. Ella graciously forgives her stepmother and leaves with Kit. Lady Tremaine later departs the kingdom with her daughters and the Grand Duke.
At their wedding, Kit and Ella are crowned as the new king and queen. The Fairy Godmother narrates that they become the land's most beloved monarchs, ruling with the courage and kindness Ella has promised her mother, and they lived happily ever after.