• Carl Maria von Weber. Romantische Oper in three acts. 1826.
• Libretto by James Robinson Planché, after the poem Oberon by Christoph Martin Wieland.
• First performance at Covent Garden, London, on 12th April 1826.

Oberon and Titania have quarrelled over the matter of male or female inconstancy and will be reconciled when a couple constant through misfortune can be found. The Emperor Charlemagne has ordered Sir Huon of Bordeaux to travel to Baghdad. There he must kill the man on the right hand of the Caliph and kiss and marry the Caliph's daughter. Sir Huon sees the Caliph's daughter, Reiza, in a dream, and is given by Oberon a magic horn to summon necessary aid and a magic goblet, that will burn the lips of the impure. By the Tigris Sir Huon saves the Saracen prince Babekan, betrothed to Reiza, from a lion. Babekan drinks from the goblet, his lips are burned and he attacks and is repelled by Sir Huon. In Haroun al Raschid's palace Reiza wants to avoid marriage to Babekan and has seen her rescuer in a dream. Sir Huon arrives. In the second act, in the Caliph's palace, Reiza is saved from marriage to Babekan, who is killed, while the court is paralysed by the sound of the magic horn. Sir Huon and Sherasmin, with Reiza and Fatima, escape by ship, which is wrecked. Reiza is abducted by pirates and Oberon tells Puck to take Huon, bound and unconscious, to the house of Ibrahim in Tunis, where the third act opens. Now Sir Huon, escaping from imminent execution through the blowing of the magic horn by his squire, rescues Reiza from the harem of the Emir. Their trials now over, the couple is transported to the palace of Charlemagne by Oberon and Titania and the opera ends with praise of the constant Sir Huon and Reiza.

The mixture of speech and music in Oberon, or The Elf King's Oath offered Weber a task that he would willingly have avoided. The work was composed very quickly, under pressure that contributed to the composer's death in London two months after the successful first performance of the opera. The overture, a well known concert opener, makes use of material from the opera and starts with the sound of the magic horn and suggestions of the fairy kingdom of Oberon. It also includes part of Reiza's song Ocean, thou mighty monster, in German translation Ozean du ungeheuer.