Prince Siegfried, a royal heir initially somewhat aimless, finds purpose encountering a crowned swan during a hunt. He intervenes when his companion Adolf takes aim; an unseen force instantly transforms Adolf into stone. Intrigued, Siegfried follows the swan to a castle, witnessing its transformation into Princess Odette.

Odette reveals she is cursed by the sorcerer Rothbart, becoming a swan by day, her curse breakable only by a vow of true and faithful love. Captivated, Siegfried immediately declares his feelings and insists she attend his birthday ball the next night, determined to choose her as his bride despite her reluctance.

Rothbart, aware of Siegfried's interest, attempts to isolate Odette and prevent her attendance. He and his daughter Odile devise a deception: Odile will impersonate Odette at the ball. Unaware, Siegfried is tricked into believing Odile (in a black dress) is Odette. He publicly pledges his love and intent to marry her.

Odette, escaping Rothbart's castle with animal help, witnesses Siegfried's pledge. Overwhelmed by despair at his apparent betrayal, she faints. When Rothbart reveals the deception and Odile shows her true form, Siegfried realizes his mistake and is devastated. He pursues them back to their castle.

A confrontation erupts between Siegfried and Rothbart. Rothbart offers to spare Siegfried's life due to the pledge to Odile, but Siegfried rejects this. During the battle, Rothbart gains the upper hand and threatens Siegfried's life. To save Siegfried, Odette offers to submit to Rothbart and marry him. Witnessing her sacrifice, Siegfried impales himself on Rothbart's sword. His self-sacrificial act creates a surge of light that destroys Rothbart and Odile, breaking all enchantments, including Odette's curse and Adolf's petrification. Siegfried and Odette survive the castle's collapse and reunite, their love triumphant.