When the Duke of Brabant died, he left his children Elsa and Gottfried in the care of Friedrich von Telramund. Gottfried has mysteriously disappeared, and Telramund has accused Elsa of his murder.

ACT I

King Heinrich has arrived in Antwerp to recruit the Brabantines to join him in defending Germany against Hungarian invasion. Telramund tells the King that Gottfried of Brabant has been murdered by his sister Elsa, and claims the dukedom. The Herald summons Elsa. Elsa tells the King how she prayed to God in her distress, and saw a vision of a knight who will vindicate her. Telramund demands that Elsa’s defender fight him in single combat. The Herald orders Elsa’s champion to appear. As Elsa prays, a stranger (Lohengrin) mysteriously arrives. He offers to fight for Elsa on one condition: that she never asks his name or where he comes from. Elsa agrees and they vow to be faithful to each other. As the men prepare to fight, King Heinrich leads the Brabantines in prayer. Lohengrin defeats Telramund but spares his life. Elsa rejoices, but Telramund’s wife Ortrud rages at her husband’s defeat.

INTERVAL

ACT II

Telramund blames Ortrud for his public disgrace: it was on her suggestion that he accused Elsa. He feels that God has punished him, but Ortrud scorns the Christian God, and urges Telramund to vengeance. She argues that if Elsa persuades her knight to reveal his name, he will lose his magical powers. Elsa arrives, and Ortrud confides in her, telling her that she fears that she and Telramund will be banished. Elsa promises to protect Ortrud. Ortrud secretly calls on the pagan gods to aid her revenge, before falsely promising to serve Elsa, and sowing seeds of doubt in Elsa’s mind about her mysterious future husband.

The Herald informs the Brabantines that Telramund is an outlaw, and that Elsa’s knight – the newly-crowned Protector of Brabant – will lead the Brabantines into battle for King Heinrich. While most of the Brabantines rejoice at this news, Telramund promises a small, resentful group that he will help them destroy the stranger.

The wedding celebrations are interrupted by Ortrud, who accuses Elsa’s knight of sorcery, and declares that Telramund was wrongly accused. Telramund bursts in and challenges Lohengrin to reveal his name – but the bridegroom replies that he will answer only to Elsa. He appeals to his bride, who promises never to doubt him, and the wedding celebrations continue.

INTERVAL

ACT III

Following the wedding, bridesmaids accompany Elsa and her knight to their bedroom with a song. Alone with her husband, she recalls how he came to her in a dream – and wishes she could know his name. Despite Lohengrin’s reassurances, she becomes increasingly fearful that he will leave her, and hallucinates that she sees the swan returning to take him away. Unable to bear it, she asks him who he is, and where he comes from – and at that moment, Telramund breaks in and attacks Lohengrin. Lohengrin kills Telramund, and orders Elsa to go before the King, where he will tell her what she wishes to know.

The body of Telramund is brought before the King by the Brabantines. Lohengrin is summoned, and he informs Heinrich that he can no longer lead the people as their Protector. He admits to killing Telramund, describing how Elsa broke her promise to him, and reveals his identity at last: he is Lohengrin, from the land of Monsalvat, and his father is Parsifal, guardian of the Holy Grail.

Now the Grail summons him home. Elsa begs for forgiveness, but in vain: the swan returns. Lohengrin reveals to Elsa that the creature is her brother, Gottfried. Had she kept her vow, Gottfried would have been restored to her after a year. Ortrud reveals that she turned Gottfried into a swan, and that the pagan gods have had their revenge. In response, Lohengrin prays to the power of the Grail, and Gottfried resumes his human form. Lohengrin departs.